Bit of a late addition to the topic, but am a new player and noticed it. I think how many players stay for 2 years isn't that interesting. What'd be more interesting to me is how many stay for say 50 or 100 games.
As mentioned the lobby can be a fairly hostile place for new players. I'm at about 50 games now and around 900 rating, but still 'grey', which means I still get excluded from a fair amount of games. Now, I understand, because balancing with grey players can be difficult. But it doesn't help new players get into the game, and feels discouraging.
That said, the game is great, and the community is passionate, and a fair amount of resources are available. I find Jagged's stream an excellent resource. And the 1v1 and 2v2 matchmaking are a lot of fun. Also a bit discouraging for the first few games perhaps, but as long as the rating gap isn't tooo large, it can be quite good/educational. And some higher rated players will give you some advice after or during the match, which is awesome.