Been rewatching Star Trek: The Next Generation, and something that jumped out immediately at me is that these are not normal, present-day people. They are weird, ethics-obsessed utopian naval officers with a very particular culture and outlook that's not our own. They don't act like us, talk like us, and for the most part they don't really think like us. In fact, many of the aliens they encounter resemble modern people much more than the Federation - this was also the case in the original series, and both series use the Federation characters to comment on modern day society by imbuing alien species with our modern attributes (petty squabbles, greed, various culture wars, etc) while the Federation characters observe and comment from a fundamentally different viewpoint. (A very similar framing is used in the Iain Banks novella State of the Art.)

DS9 mostly continues this, although since it doesn't take place within the Federation proper there are far more characters that more closely resemble modern-day people. Even then though, characters like Quark or Odo still embody a fundamentally different sort of thinking and mindset presented as alien to us. Voyager always struck me as a bit more TV land and it takes another step towards representing modern people via the Federation, and then in the most recent Star Trek series like Strange New Worlds the characters are for the most part just Modern TV People. They occasionally espouse some science fictional ideal, but for the most part they talk, act, and think like modern people - or at least like the version of modern people you get in the hyperreal of Television Land.

Instead of the Federation being presented as a somewhat familiar other that the show presents as an aspirational goal, most modern Star Trek characters wouldn't be terribly out of place on any other TV show in the modern day. It's a massive failure of imagination and imo the central reason that Star Trek has withered as a series.

(Addendum: Key element here also seems to be the death of Gene Roddenberry. My understanding is he was extremely emphatic about Federation characters not acting too modern or demonstrating modern vices, interpersonal flaws, etc. He died partway through TNG’s run so I suppose there was a lot of momentum baked into production that gradually faded as the property changed hands.)