Most of the issues in this thread relate back to the fact that the genre itself seems to be moving away from trinity-based role designs. If FFXIV was released for the first time today, you might not even have dedicated tanks and healers. You'd probably see more of an action MMO setup with players primarily managing their own health bars and a few 'support-orientated' dps for players who are really into that sort of thing.

Part of this just reflects how players have changed from 20 years ago. Progression isn't tied back to your community. You can find groups at your specific progression point with relative ease, and just jump into doing content on demand. As a result, we're less tolerant about waiting around for other people to work through their mistakes. Nobody wants to sit around and watch a so-called 'main tank' learn the pattern of cleaves on a fight or how to move a boss. You might want more intricate heal checks, but players aren't going to sit around and watch you learn how to manage your resources and figure out your timings in order to do so. Mechanic checks are more egalitarian. You're either at the prog point, or you're not and we silently disband. Your role choice doesn't matter.

The downside of course is that these roles still exist within FFXIV, but their function is essentially vestigial by this point. Tanks are simplified melee dps. Healers are simplified casters. This suits some people, because you have alternative roles that are less competitive and less demanding. But it's also deeply unsatisfying because supports just don't have the impact that draws people to play them in the first place. I don't really know what the solution is, short of giving tanks and healers more opportunities to set up their teammates to do more damage, either through boss positioning or unique support actions (like raidwide movement actions).

Homogenization is an unavoidable phenomenon and just reflects the fact that the community will always compare relative job performance. So there's naturally a convergent pressure to eliminate differences. This is more pronounced on tanks and healers because there's fewer of them, so the instant you add a unique or exciting action on one job, everyone else will be clamoring for its equivalent to be added on their jobs. There's this sort of arms race going on at the moment where tanks progressively add more and more redundant layers of defensives just to keep up with the competition. This is less of a problem for offensive actions because they just need to be numerically balanced.