I know that “Space, the final frontier” went from “where no man has gone before” on TOS to “where no one has gone before” on TNG for reasons of ‘let’s try to make this less sexist’ but still nobody thought to question the whole idea of the frontier until the DS9 pilot. And then no other show followed up on that except maybe the hints on Voyager and Enterprise about those ships destabilizing an already existing situation everywhere they went
Your recent posts like this one ^^ is what reminded me about my essay which included Imperialism and the Federation.
I think a big part of the issue is narrative framing. The characters on older Trek (not always but sometimes) argued more. They took perspectives on parts of the debate. The newer Trek has a lot of the same hooks in the storylines but the thrust of the plot tends to push the same agenda (which isn’t a reflective one). They don’t tend to question whether they are right anymore, they just assume they are and go from there.
I mean Discovery began with the Klingons at least making the point about cultural homogenisation, and the way the Federation spread. That point was lost in the show (narrative framing) because good guys vs bad guys is easier to sell? I don’t know.
It’s hard for me because I have all of this ^^ in my head so I tend to see it, whereas it might not actually be there so much.