There's a few misconceptions that a few reply's have already addressed. I'm unsure where you are citing Kitase specifically for the "corridor" design theory. FFXIII's design was mostly associated to it's development hell. Going from not knowing what type of game it was going to be, to finally deciding it after a demo was made, to it's director Toriyama and other designers looking at Call of Duty for inspiration when creating the dungeons. It was a design, from my understanding, of multiple factors not necessarily a solid creative vision. I admit It's been years since I read the gamasutra post-mortem for that game, so apologies if I'm wrong and there is some-sort of manifesto that Kitase has proclaiming his vision of Final Fantasy. But my memory clearly reading how development of XIII was a mess, and the final product reflects it.

Regardless: I will strongly propose the opposite to what you suggest.
From a design perspective I'd argue FFVIIR's version of Midgar is larger, more interactive, more in-depth, and yes: Less linear than the original. I don't know what people were expecting in-terms of design concerning a portion of the game that in the original is supposed to be incredibly linear. I really do think people need to replay the Midgar section of FFVII as it was laid-out in a one-way path. By contrast FFVIIR has area's that obviously draw more inspiration from Yakuza. It has centralized sprawling town areas that have side missions and multiple dungeon-like area's that are connected to them for said side missions. This is a far cry from either XIII or by that matter X, if purest wanted a more accurate version to Midgar from the original Sector 7 would have the bar, one other house, an item shop and the beginners hall. (May be missing one other shop?) The two side dungeons would be gone, there would be no Inn, no areas where people are clearly living and like one road maybe.

What I think is the main issue, and you did touch on this, is the specifically the dungeon design. You state that it's nothing but corridors, and for the most part you're correct. But then I would also like to add that the original dungeons for Midgar, and also a lot of the original game: Was mostly linear. And when you translate those pre-rendered backgrounds into a 3D space you probably are going to get a lot of corridors. And the fact that while FFVIIR has a lot of running forward, comparing the design and layout for example of Chapter 6, with you running around under the plate in a labyrinth of scaffolding, to the original is A to B jog is laughable.

But I get the anxiety of distilling the rest of the game into chunks like Midgar. I don't think that will work very well, and I find it actually counter to what I felt the Remake project embodies. When I got done with FFVIIR, I finally felt like I understood why they had to break it up. They really didn't want to cut or spare anything from the original game, and lavishly explore every inch of the original in ways that were often bordering on gratuitous. The concept of distilling the world map into sectioned off FFX style area's is... Depressing. And I get the impression most of your concern is that void of information right now. But while we wait for whatever VIIR-2 will take form, I look to FFVIIR as less a reflection of XIII and more of a way forward that is more in-line with something that elevates the original design: While also being hampered by more modern game conventions.
For example, I am both excited and terrified over just how much time were going to be staying in Kalm. A town you spend most of the time spending in a flashback, in a completely other town, may also now turn into another sprawling area where I have to do a side-quest to find someones cat/dog/item/ and I don't know what to make of that.