why FF14 don't do more collabs?

[Unholychinchilla]

Pso2 bags the difference. It's just costumes and nothing more but it works.

You're missing the point. We're not talking about quantity of content being low but the quality of it not being up to the games usual standard. Rather than the complaint being "It's just costumes" you face the complaint of "The costumes look terrible, especially compared to the other glams in the game".

That would reflect badly on both XIV and the collab partner. Neither party wants that.