As a video-game, it's not really special.
The combat is a bit repetitive, though commanding all of the moves of your team is a lot of fun and the team combos look good.
It's not a hard game, the difficulty options menu is also very detailed and helpful to customize your experience.
The achievements are on-topic and simple enough that you can complete 100% of them with a single playthrough.
The level traversal is mostly linear, you only ever deviate from the main path to find new outfits or upgrade materials, which are plenty enough to fully upgrade your character before ending the game.
The character designs are also great, definitely better than the movies, I only noticed it when comparing the collectible outfits.

However, I'd say that it is almost unfair to judge GotG's game on its ability to be a game. It really is a very long movie (or TV show) about the Guardians of the Galaxy; so it follows that it should be judged by its accomplishments as a story of the Guardians and compared against MCU movies, and action movies in general.
It is a good action movie. A 20-hour long story about found family, grief, fatherhood, PTSD, and so much more.
The writing is compelling and takes the story in many different places, letting every character have their own arc and their moments of growth, without stepping on others' toes. Every element presented gets its time to shine and Chekov's Gun always gets fired.
The voice acting is great (I especially liked Mantis). The OST works well, and the needle drops are phenomenal, as we are accustomed to with the GotG movies.

As a video-game, it's probably a 6/10: nothing special to find in the gameplay or the exploration except for some interactive environment puzzles and stylish combat.
As a movie and story about Guardians of the Galaxy, easily a 9/10: arguably better than the movies, due to its long runtime and breathing room for every character and the plot.

Note:
- the MoCap is great (especially Gamora's), the character expressions are awesome
- Space llama
- A couple of short scenes had really low framerate, but the optimization is generally well-done

Completing all historic challenges and a pro career will show you just how much this game is jank. I much preferred MotoGP 2004 to this barren, soulless and empty mess.
At least there's no microtransactions.

The open world and non-linear "storytelling" do a greater disservice to the game than the poorly designed perspective puzzles.
The game is entirely too long, with 11 different zones that vary way too much in difficulty and events that seem designed to waste your time by watching water drain or rise or moving platforms at a snail's pace.
I was about done after about 10 hours of this game, but 5 hours later I found the 15-minute-long lecture on solipsism and as soon as that was over, I decided to put an end to my misery. I can't be arsed to find every useless tape or every dorito panel scattered around the island.
It's a decent puzzle game, but there's no point to any of it. It's about everything and nothing at the same time. Try it if you like connecting dots.

I liked James Burke, Richard Feynman and Ashley Johnson. ♥♥♥♥ tetris.

I'm not gonna spend an hour trying to dissect this game just for a review on steam that nobody is gonna read.
You just need to know that it is an actual game, made for people that are willing to listen when art decides to talk to them; it's also quite serious despite being drenched in satire from start to end.
Metaphores, parallelisms and a whole lot of heart wrapped up in a neat and very atmospheric golf game.
The devs even gift you the OST once you finish the game, which is awesome. Radio Nostalgia from Mars is my favourite radio station!

better than Shadowkeep and Beyond Light, far worse than Forsaken or Taken King

Update requires restart.

Monetization sucks, the FOMO "challenges" are really bad and there's pretty much zero customization if you don't want to get your wallet out. Even when you DO pay money, the majority of the Season Pass and the current Tenrai event (called the "first free event" meaning that there could be paywalled events) are filled with worthless stuff like xp buffs and challenge swaps.

The sandbox has an ungodly level of polish and the game feels so good to play. It's a shame that without anything worthwhile to chase people will probably jump off sooner or later.