To Square Enix, these are the reasons why I am currently unsubbed from the FF14.

[Zojha]

Tanks and heals cannot hide a mistake easily, a dps can [...]

I honestly don't think that matters. You can play any game where mistakes of DPS are blatantly obvious, people still prefer DPS. You can go and play games where DPS have a bigger responsibility, DPS are still the most popular.

And truth be told? DPS is just the natural mode to play combat games. Most games revolve around killing stuff, not trying to hold mobs off other people as living bait or healing injured people. And the way to do that? Dealing damage. You'll find that throughout all the genres, from turret defense, over shooters, RPGs, Bullet Hell games, strategy games, fighting games etc etc. Even some "healing" games have you achieve your goal by dealing damage to germs. It's rather natural people gravitate towards that.

Some indie game devs seem to have realized, I just recently saw "Healer's Quest" on Steam, which seems to be all about breaking that up by progressing "without" dealing damage - Though your "party members" still do, as per usual. Kinda a necessity, as without damage, no damage to undo, i.e. no healing. It's not exactly a common type of game, tho', more of a parody.