In 2015, there was about 14% platinum players.

Right now, there's 7,7% in plat and 1.9% in diamond ( previously 3,3% in 2015 I believe ).

If anything, dynamic queue stopped the boosted animals from getting higher ranks because the game is fairly harder, due to improved teamwork of the premades, which is a good thing, this is a team game, and it should move toward that more and more, while encouraging 5v5s over solo queue.

Back than, you could be a very average player, and with a 50/50 win rate you would climb the rank slowly ( diamond V players with 2000 games ), now if you're 50/50, you won't really climb anymore, that's why there's so much complaining, there's a lot more average players than good players.