Sorry I did not make myself clear. My demo impression that I posted much earlier was of cos the demo, but my impression posted yesterday was after watching some 4 hrs of streaming of the full game from 2 sites. I quickly skimmed those videos again and you are right, there wasn't much of the enter room, clear enemies, exit (ala the good old double dragon) style of game play. However there are actually a lot of 2.5D, even in exploration, from the beginning of the game, the demo area to the sort of tree house area.
There is green grass fields in the game, with pond you can fish and small waterfall, but these areas are among buildings, roads, rusty cars and more damaged buildings. It's not the same feeling you get when you see 'nature' in the open. Instead there are just as many areas filled with sand, looking like desert. I am not expecting a colorful, vibrant, lively post-apocalypse world like The Last of Us, Horizon Zero Dawn, or even Destiny (the locales actually reminded me a lot of Destiny and Darksiders), but here even the amusement park looks dull.
And talking about dull, the whole game looks monochrome or sepia. It's color palette consists of mostly just grey (apart from the aforementioned green used for grass), making Gears of War look like a kaleidoscope. Even the menus are just plain dirty greenish-yellow. The whole world, everything you see, is draped in a layer of mist. Maybe there is a story explanation for it, the game's in Japanese and the commentators didn't mention it, so I don't know. But the net of it is that every location looks extremely dull. I looked back at some video of Drag-on Dragoon 3 (or Drakengard 3) and even that looks a lot more colorful. I know, it's the art direction they are going for, but it's very boring art direction. I know, it's the director's 'thing', it's his 'vision', he's going for the depressing look. Well, he has outdone himself this time and succeeded in getting to me.
As for the boss fights (saw the one at the amusement park, what looks like opera singer with big skirt that appeared in many trailers, as well as some smaller bosses like the tank and the naked guy), while the boss design is interesting, the actual mechanics feels been there, done better, in little indie games like Furi (complete with bullet hell) or Titan Soul.
PS. No offense meant nor taken, we are just expressing our own opinions. Mine's perhaps less accurate since it's not first hand but it's just how the game feels to me. I watched the full game streaming, after being disappointed by the demo, cos I wanted to see if there is something beyond the demo that can spark my interest and bring back the good old ps3 Nier memories. Sadly as it is I won't be picking this up any time soon.