For MMO / dungeons I'm not entirely surprised, though I feel there might be some ideas that could fly with the culture (just probably not in a standard concept).
However, given a single player RPG.... I mean.. clearly No? There are a lot of non-linear dungeons in absolutely famous, profitable, games. There is also linearly non-linear designs, which I just made up the wording, but take those dungeons where they have puzzles and wrap arounds that you're mostly supposed to go through by a particular path, with some branching, and as you explore via metroid-like/castlevania-like unlocks the place gets larger and fuller while also unlocking QoL. Souls, GoW, and even sometimes Bethesda games have this. I would be disappointed if someone tries to argue a hub in a zone in FFXVI counts as that since you start at the hub and branch out in one direction, just cause that hub ends up with multiple branches imo doesn't compare to a game that is wrapping around itself like a key ladder kicked down in a Souls game (I think traversing through the space vs using it like a train station might be one of the reasons why it doesn't, imo, apply).
Because it's a negative comment I have to remind that I do like FFXVI, but if someone was like 'quickly pick something you think they need to do better next time' I would definitely say level design is one of them, at least in gameplay regions. Not visually, but mechanically. The level design is just simple, it's not cleverly simple, or open and free, it's constricted and simple. Hilariously, in non-combat regions they have many layered multiple pathed areas, many town / airship spaces are very non-linear (and took me a little bit to explore, like Lostwing lol).
I wouldn't say simply having loop backs or useless multi-paths makes it exciting, as that might be a take away and that's not the point, but I would personally lean to either open and freeing (doesn't mean purely open world but, not feeling like I'm on strict rails) or cleverly linear (like GoW). Currently it's neither freeing (loads of invisible walls) nor feels very clever, that sounds like an insult and is not intended as one (opposite of clever might sound like a pejorative, I am NOT saying that but probably am saying 'simple / straight forward' feeling).
There are a lot of games with good level design but some things that stick out to me are some of the Souls games (in general, but like Sens fortress maybe), GoW (new ones), Dishonoured (especially that mansion, may look at Hitmans or Deus Ex for multi-approach as well), Prey, Metroid and Castlevanyia (but keep in mind it's 2d... doesn't translate as smoothly), perhaps Portal for puzzles that unfold themselves yet don't make you feel handheld, etc. Lots of good examples but those ones popped into my mind at first.
I usually play in a assuming design sweeping pattern by that I mean I assume the developer's thoughts and work through the space in an attempted efficiency (you can see the design decisions that guide players, lights, shapes, halls, etc, sometimes literally if a marker system is in place, and choose to go the other direction and often be rewarded), and imo the level design feels really simple and not Dark Souls in comparable level design tier.
Opinions are like chocobo butts though and we all have one so we can agree to disagree and that be fine, but my sweeping pattern for this game felt like I was using really simple mental algorithm and no 'exploration'. Vs some of the other games I listed, or Dark Souls as you referenced.
As posted above though I would caution simply responding to the feedback with 'make it more convoluted', or that it has visual issues.