i think a lot of postwar architecture boils down to an ego trip
I mean...kind of? The theory behind these "modern art" pieces is wild. Eisenman's collection pulled upon broad depths of theory. People who understand the basis of thought will understand the ego and appreciate the work.
I think a clearer distinction is that architects in the modern age are finding a stronger expressive link in their work rather than to the client. That's the distinction I made above between Alexander and Eisenman RE: Eishin vs. House VI. It's also the dynamic of public opinion that KB got at above - in short, public opinion barely matters to whether something gets built or not. In the case of public-facing architecture, the weakening of the non-paying, only-observing client link appears as (and is!) a strengthening of the architect's ego. With public/client opinion backseated, any artist will create with and from what they know, which will always be an ego-expression. There's no way around it.