tl;dr varsion:
Compared to OMD!2, this game is as twice as expensive (I've pre-ordered both OMD!2 and OMD!3), has less content and is full of bugs. I'm not familiar with Stadia version, maybe all issues are inherited from it, maybe it's unpolished Steam port, can't tell. Surely the budget was very limited, there's quite a bit of rounding the corners and most likely beta test were cut short.

Now, time to elaborate a bit :).
Gameplay is pretty much like in previous games. There are changes, like now every enemy costs 1 rift point (no more armoured ogres costing 10), there's no penalty for death (though it feels like it's easier to die, probably because of these pesky ranged mobs) and (the controversial one) almost all ranged weapons can register headshots (including blunderbuss). It makes game easier compared to previous two (it seems like trend since OMD!2 was easier than OMD!). Not really a deal breaker, there's still Nightmare mode around. I've noticed that enemies no longer speed up when close to the rift after patches, it seems like someone thought it wasn't good change (or it was just a bug). There are some strange changes in equipement. For example, Lightning Ring (which is now trinket, not a weapon) abilites are now split into two items - ring is used to summon thunderstorm while chain lightning is Chain Lightning Staff's ability. Some traps are altered - for example Grinder no longer recharges while idle but not completely drained - which sometimes makes these less useful. Some items, like Coinforge :(, Vampiric Gauntlets or Polymorph Ring (whyyyy...), are gone. Unfortunately few useless ones still are here (Ceiling Pounder). Interface is much "lighter" than in previous games, which is good, but at the same time it doesn't provide "health bars" for almost all traps (except Grinder and Barricade) that indicate recharge time or charges left in case of traps. Furthermore, it doesn't accentuate differences between player characters by different mana/health bars' lengths (which have different mana and health pools, from tanky Vorwick to squishy Cygnus). Just like items, some enemies gone gone too. There are no more Fire/Frost Ogres, Swamp Trolls, fliers are all shifted to DLC campaign levels. There's whole "orc-reskin" class of enemies which are all immune to fire - this outhright makes all fire related upgrades, traps and weapons obsolete because these new enemies come in hordes, just like orcs.
New "big thing", War Scenarios, are, um... Aside from bosess (which are pain in the rear in some cases, not all though, for example the one in Dragon Boneyard can be left to be mowed down by killbox which player has set up by the final wave which is boss wave), there's not much. These maps are larger, there's lots of enemies but that's all. Beacuse of huge amount of starting cash and huge number of enemies, it's easy to set up efficient killbox using regular traps and ignore expensive war scenario traps completely. The fact it's easy to set up kill box early means that getting par time on these levels is extremely easy, unlike regular scenarios, where par time is quite strict. It's noticeable on levels like Sludge Shelves or The Basement, on these maps being in right spot in the right time is essential. It's not often though, most maps allow funneling enemies into single area (having single rift on every map helps a lot too, this is shame actually because previous game had lots of maps with multiple rifts) where it's easy to build efficient "death zone" for orcs and their allies.
Visually the game is ok, I guess. The OMD!/OMD!2 style is preserved while all bells and whistles are (more or less) upgraded to nowadays standards. Sometimes these get in the way - having lots of lasers, traps spilling ice, acid and whatnot, player tossing frost bolts - it all obstructs the view to the point where sometimes it's actually hard to see enemies. The cinematics are no longer hand drawn stills, these are kind of fmvs now. It's ok, though video after last level is... underwhelming - not entertaining and quite basic. The Drastic Steps videos seem to be much better, at least these bring that not too serious approach from previous games. Which is not present in main campaign, unfortunately. The story is pompous, lacks that lighthearted approach. It starts with "the earthquake" (which is fine), rolls out some retrospection levels and then it loses all tempo and becomes dull. All the hilarious bickering between characters from previous games are gone, instead there are two uninteresting wiseass teenagers and one "mother figure". Drastic Steps fixes this by bringing back that chemistry between Gabs and Max, but that's just short 5-level campaign. There are too few nonsense oneliners thrown around by player's character, even in case of Max. Personallly, I don't enjoy ost as much as in previous games. It's a bit in the background now, less noticeable (lacks that "something" which made me to listen to ost outside of the game in case of OMD!2).
"Unfortunately", I've left the worse for the end. There are some weird design choices. For example option to reset scramble mode is placed not on the scramble mode screen but in the game options. Speaking of scramble mode, buffs and debuffs are grossly unbalanced - there are crippling ones (boss spawning at each wave, doubled cost of all floor, wall or ceiling traps), almost meaningless ones (barricade cost incerased by 50%) and overpowered ones (item dropped after every kill by headshot). The ESC key doesn't work in some areas in menus. The spellbook looks plain and unfinished - at least upgrade "cards" could use some artworks. Texts in these rectangles often align weirdly or stick out of text area, not too mention font scaling which sometimes makes upgrade descriptions barely readable. The ragdoll is grotesque - severed limbs fly like helium filled balloons. Some enemies are still "colour-coded" while others blur into shapeless blob (which makes threat assessing a bit difficult). And the worse - the bugs. These range from nuisances - like occasionally wrong images on loading screen or low res images in spellbook (or broken translation, broken score display in particular non-English versions) through hilarious ones (like ceiling/floor trap which can be placed partially inside the wall or enemies just standing and doing nothing unless player gets close to trigger their aggro) to game breaking ones. These are really painful. Sometimes enemies clip through barricades or smash these for no reason (it's easily replicable on Colosseum where Gnoll Hunters, which should ignore barricades, aggresively attack these if these are placed in particulas spots). Sometimes (it seems to affect enemies which have been frozen multiple times) player's weapons stop dealing damage - I've even encounererd few orcs that were literally invulnerable - nothing could harm them. Quite often game stops to respond to keyboard commands for few seconds. On some maps crowd control items that affect enemy pathfinding don't work at all - on these levels charmed enemies still walk (end enter) towards rifts and run through Jar of Ghosts active effect.
I haven't play multiplayer yet - people say it's broken in many ways, which (if it's true) is step backwards when compared to OMD!2.
To sum it up, OMD!3, even after 4 major patches, is still far away from pretty much bugless OmD!2 (at the release day), it's downgrade in terms of contents and biggest novelty is just a knick-knack. Scramble mode is much better at bringing fresh air into franchise, but, as I mentioned before, it needs some serious tweaking. If you really want to experience OMD! style gameplay and you've never played any game from the series, go grab OMD!2 (and maybe OMD!, at least to unlock Classic levels in OMD!2), it's much cheaper (even full package), bugless and has much more contents. If you're fan of the series, I recommend waiting until RE fixes at least the worst bugs. Or maybe just wait for OMD!4.

I never thought I'd say something like this... This game is horribly underpriced! Price set at 0,99 €/$/whatever places this game in the same price tier with shameless Plants vs. Zombies rip-off and some other terrible games I won't mention here. This makes it easy to overlook this little gem. It's exactly what description says - minesweeper in 3D with few twists here and there. So if you're minesweeper fan, most likely you'll enjoy this game.

Short version:
Don't buy, bad game, waste of money.

Longer version:
Earth 2140 was solid RTS game, Earth 2150 (TMP/LS) was very good one. Earth 2160 is awful. I'm big fan of the series, but honestly, I can't say many good things about Earth 2160.
pros:
+ graphics
+ return of infantry units
+ experience is gained by pilots rather than vehicles
cons:
- balance (Morphid air fleet is virtually indestructible)
- cliched story (in E2140/E2150 story didn't actually matter, in E2160 we get mix of all sci-fi movie themes you can imagine)
- pitiful voice acting (actors don't even pretend to try)
- missions ("good old" objectives like "get from point A to point B" or "gather resources and wipe enemy base(s)")
- "improvments" to good ideas from E2150 (research tree now fits into one screen, too bad it looks as if someone barfed on the screen, different armour types introduce mess and confusion rather than diversity)
- soundtrack (it isn't bad actually, but there are very few tracks that are faction exclusive, it's huge step backwards compared to Earth 2150)
- activation (it kind of made sense when game was released, but now it's just ridiculous, on the other hand - LC campaign is broken and, as far as I remember, multiplayer servers are down, so going through activation process is pointless)
- AI (I was playing last mission in ED campaign on hardest difficulty and I was surprised how AI was "sending small groups of units to certain death", in the same mission AI ground units were getting stuck over and over in narrow valley)

Yes, this game has it's unique visual style. But honestyly, I can't recommend it. There's lots of boring backtracking and game is very easy. Even final boss doesn't pose any challenge. If you expect that exploring all corners of the map will be properly rewarded, you'll be disappointed. You'll get few very short cinematics and handful of artworks (and of course upgrades for armour and basic weapon).
It's not total waste of time, though. You'll have lots of fun before novelty effect wears off. I'd give it 5/10.