Honestly I feel like a non-insignificant chunk of the general population that says it's among the best games ever (no, not any one person in particular) just feels the implied need to defend buttbot.
It's really not that good. I mean, the combat is good, but it - like so much of Platinum's catalog - is just a watered down Bayonetta again. Still fun, sure, but when I see people claiming it literally one of the best ever, I have to think a certain number are doing it for more...deep down reasons, even if they'd not admit it. As for the ending... the idea of being depressed about the world having no intrinsic meaning?
I don't see what's so depressing about that, the world is what it is.
The world goes on, predetermined or not.
You/yourself chooses what matters, it's not something that is inherent about the universe.
Why do robot soldiers in a great war all look like sex dolls and 12 year old boys? If you had robot soldiers wouldn't they be a bit more practical? My main take away at the end was, "wow, all these robots would be better off dead and why does any of this matter?" I found none of the characters likable, the gameplay started fun but got old after a while, and the story was completely uninteresting to me.
