The lack of a "sense" of progression is the game's current problem. I get that they're trying to make an esport out of it hence they don't want anything other than cosmetic progression, but there has to be something else. CSGO survives with just ranking as progression, though I believe it's grip on players is more because of its simplicity and nostalgia (and crates?).
It doesn't really matter to me if the art direction is cartoony, it's been mostly that way with Blizz anyway. They want a wider demographic. They want more people to play their games. I never had a problem with TF2, that game is comical and lighthearted, it's a little harder to get frustrated about it when you lose.