DOTA in the beginning for everyone I've spoken to has a very big learning curve, this was back in 2011 when I started. With the advent of the learning/training ground and the Items page as well as training with bots, I think it has improved new players ability to pick up the game mechanics faster although to get good at anything you need to put some serious amount of hours behind it. What I did was went through the heroes one by one and tried them all out to learn what they did and how they are useful in lineups. what also helps is watching the international and other tournaments to see what the professionals are doing that maybe you never thought of doing.

I used to have some dislikes but I don't play as serious as I once did, and Valve has made large strides in the matchmaking engine as well as the commend and reporting features. I almost never see couriers being fed to the enemy team anymore as this once was rampant when someone would rage in a game, or when someone would just run down mid feeding over and over. These issues may still persist but I do not play in the bottom brackets so I'm not sure if new players fall victim to these behaviors.

an improvement if there wasn't already one is to have an OPT in or out to be queued up with new players, or I think matchmaking can't be played until you have 50 or 100 games under your belt, or maybe if you have a win rate over 75% if you are less then 100 games played.

I don't enjoy turbo that much because I feel like it maybe exists for new players to play games quicker but there is never a handicap for more experienced players, I think it would be good if there was another option for new players to have their own all pick section, and if someone completely crushed them they could report that player and with enough players reporting that player have them removed from playing in those new player servers.