A couple of points.

Damage dealt is always an important consideration, irrespective of role. Nobody is saying that tanks should do more damage than primary damage dealers. But we still need to do relevant damage. This is because:
1) Your ability to clear fights is gated behind raid damage output.
2) Every tank in this game functions in melee range, and damage output is a function of melee uptime. If tank melee uptime doesn't matter, we can just go invuln mechanics in the corner while everyone else does relevant damage.
3) The entire appeal of tanking is built around going toe-to-toe with the boss. This, in turn, is built around you being a credible threat. If you're beating on the boss with a foam bat, why are they targeting you? Because they're programmed to do so?

It's obviously not the only consideration, either. From a fight design perspective, tanking in this game is sub-par. The reason is because we've moved away from positioning and movement mechanics in favour of self-positioning bosses. It's the MMO equivalent of a rail shooter. This is a historic problem with Square Enix. When you become overly fixated on the dramatisation and story-telling elements of the fight, it stops being a game and it starts to turn into an extended cutscene. Mash square to power up your Guardian Force.

Let us position the boss. Let us move the boss around. Let us dictate the course of the fight. Your dramatic fight choreography may not play out as planned, but at least it'll be enjoyable to play, not watch. Give tanks back their autonomy. Let players control how the fight unfolds. Not you. The players.

There's another issue here. The developers seem to want to make tanking more accessible. But it's all backwards. In dungeon content, tanks are expected to know where to go, how to pull, and direct the flow of the fights. That's intimidating for very new players, sure. But when you get anywhere near raid content, it's reversed. You have auto-positioning, auto-tanking bosses. You're irrelevant. It should be the opposite: easy to pick-up and get into, but difficult to master.

I feel like the game that the present fight-designers are trying to deliver is very different from what tanks, especially those who have spend time playing western MMOs, are looking for. Which is fine - maybe they've analysed the market and such players aren't important to their bottom line. Regardless, I think that they would be better suited just sticking to healers and dps if there's no room for high level tanking. Just create a quicktime event for one of the dps when you want the big tankbuster moment to happen for dramatic effect.

Tanking needs to be both relevant and accessible. In trying to make tanking accessible, the devs have failed at both. If they care, the above problems are the ones to fix.