Then why not explain what makes it bad, similar to how I explained what makes it good, instead of just less = bad/backtracking. Because that sounds like pretty simple minded reasoning. Metroid, Resident Evil, Yakuza, etc have you backtrack with purpose.
Every power up you get in Metroid and every key you get in Resident Evil could have just been meant for a door you've never seen before. But that would take away a big part of those games for me. Associating an area with a number of different things. And that moment when it clicks in your brain.
It's not inherently bad game design to revisit the same area multiple times. It can be a design choice. And a good one at that.

I'll take the first time I visited the closed and intimate space of Kamurocho in Yakuza (which has you revisiting key landmarks several times, like in Nier) over the vast majority of worlds I've experienced in other games.

And you are incorrect about the Amusement Park.
It was the stage for several side quests. Including the theatre play quest.



And it was used as the backdrop for the end of the Wandering Couple questline.



This scenery is the first thing I think of when I recall this questline, precisely because it played out with the Amusement Park in the background.

Speaking of which, that first visit you're referring to was easily one of the most memorable sceneries I've experienced in a game, due to the aesthetics combined with the dynamic whimsical music that changed as you got further and further in, which gave that area a very unique atmosphere.
So even if that area had only been the stage of one story (and it was not) it would have done more for me that 20 areas in another game.

Same thing with the Flooded City area.
It was the stage for several of the most important moments in the game.
But it's a bit bizarre to hear you complain about its size, as if you can't appreciate a smaller more intimate secluded area for what it is.
If you designed an area, it would never cross your mind to intentionally make an area smaller? 

There seems to be a pattern with your thoughts on level design.

Fewer = bad
Smaller = bad
Linear = bad

The "bigger is better/the more the merrier" mentality.
So yes, this is probably not a game for you.

And it sounds like you didn't do many of the side quests. Some of them are fine to skip. But some add important context. For example, and without spoiling anything, one side quest introduces you to some people who have some distinct clothing. There's a moment in the main story where they are the only people you could possibly recognize. Doing so made the scene emotional to me. But if I hadn't played the side quest first, I wouldn't have had an emotional attachment to anyone in that scene.

And several of them contribute to the world building I described earlier.

I think critique about Route B is fair.
They could have probably done that in a more condensed manner. But I think I understand what they were going for.
Which is to have the player view 2B from a different perspective.

The game will be getting a physical release, with reversible cover art:

The file size on eshop comes in at 10.9GB, and there's no "download required" tag on the box, so it seems to be all on the cart as well.