classicpeople are into hearthstone and that game has some pretty wonky card mechanics and there's quite a large number of cards. Granted its a card game not a fps, but its a similar concept. FPS games probably benefit more from being simple, but a majority of tf2 weapons are silly and gimmicky anyways just like a majority of hearthstone cards are gimmicky and not used in professional play.
well in hearthstone you have a turn to read and see whats going on...
in a tf2 match you could see literally a dozen of different weapons at once