I want to start off by saying I agree completely – nay, ardently – with this observation that conversation on the Fediverse is largely pathological because there is no sense of people having spaces that are theirs. There's two important parts of this.
There's the "flatness", as you've put it, @irenes: the user experience here simply doesn't communicate that there are different spaces one is moving between. Or perhaps it is more accurate to say there *aren't* spaces.