I sympathize with OP’s frustration here, as I have at times experienced a similar confusion about what exactly a deep soundstage should sound like and wondering why I can’t get whatever that is. I hope I am not being overly reductive or patronizing when I suggest that some part of this kind of confusion may come from not having a baseline expectation to work from - and instead imagining what is probably an unrealistic representation of a staggeringly deep, almost surreal soundstage that extends dozens of feet beyond the speakers. After all, that seems to be what many fellow audiophiles have, or at least are able to describe having. I have never heard such a thing in my own room, though - which isn’t to say it’s impossible, but that my particular room/system/setup likely precludes achieving it, which would seem reasonable considering the compromises I’ve had to make. The somewhat confusing psychology of not being able to achieve the perfect soundstage sometimes leaves my brain suspecting that I have no soundstage at all, and that what I’m hearing is just a pleasant but flat centered image. That psychology can be so powerful that it makes even a perfectly reasonable soundstage seem dull. A third party observer who came over to listen might completely disagree and think it sounds great.
I think I have just invented the theory of general relativity of soundstaging.