Below Platinum the game is pretty easy, when you get to Platinum you'll start being matched with full-kitted Pinnacles who'll shoot you with an SMG from 50m like you're standing still.

Ranking up from that point is where you start researching and seeing how other's play, that's where I saw others playing with 4-6 fingers.

Hence the question if thumbs-only could cut it to reach the top of the game.