I don't think people really understand open world dungeons. They don't have to be anything special (although they can be), they can hold gathering points, mobs to kill for another alternate to leveling (in closer quarter making the danger more real) and just interesting things to see and places to visit.

They do not need to be mandatory. They could add NMs to them if they kept them at v1 nm standards not xi (5 minute respawns or timers with about a 50% drop rate of w/e they drop since it wouldn't be anything critical or game breaking), special maps or some other fun, quick and simple content, they could bring back the locked chest/coffer system that was in both xi and v1 too.

Plus how awesome would it be to be able to explore Mhach further. That place is HUGE and we get a lil path. But outside that even the smaller dungeons like Amdapor could be fun for exploration and open world activities after the fact. And they do not need to all be the same and have the same things inside them. Some can be more gatherer based, some more geared to leveling, some for lore and some a combo of it all.

It would simply give the world more flavor with little extra work for the devs and enough players seem to want it, so why not?