I liked DS9 a lot and I don't feel it trod on the principles laid out in ToS or TNG. Rather, it showed their limits. The heart of the Federation was still a paradise, and humanity, by and large, still held to it's high-minded principles. However, the Federation didn't hold sway everywhere, and when push came to shove, sometimes those principles were at odds with pragmatism.
The disposability of the Prime Directive goes back a long, long way
I had liked DS9 somewhat less than the ones with the ships. The idea of exploring space and the viewpoint of humanity's precarious existence as seen from afar had a lot of appeal.
If there's one thing it did well, it was the perspective. Star Trek was for me about that most of all.
Once astronauts see the planet from space, they often undergo a shift in their attitudes.
https://en.wikipedia.org/wiki/Overview_effect <--- well worth a look Elite Cmdrs.
The Federation concept is an outgrowth of this psychology, IMHO, which comes from an enlightenment not really available to humanity till we got to space.
It was transmitted to me as a child second hand in the 60's. From footage of actual missions, and from Trek. Once you see the whole planet as a small object, and your mind makes the jump that everything is in one place, one small place, the world shrinks from many fragmented things into one thing. How to explain it? It is a seismic shift in understanding, that makes racism/nationalism obsolete as a philosophy.
It's a testament to Roddenberry's vision that he had the concept down so early on. The next step of course, is placing the one small thing where it really is.
In August 2020 anthropologist Deana L. Weibel introduced the parallel term "ultraview effect," a subjective response of intense awe some astronauts have experienced viewing large "starfields" while in space, and discussed the impact of the overview effect and the ultraview effect on astronauts' religious beliefs.
So of course I play Elite. It is as close as I can get, other than driving at 100mph in the dark with all the windows down. Some people like Sam Harris do this with psychedelics.
It changes the brain's state somehow.
it makes me sad to read comments about people counting how many of what race is on TV, to help them decide if the show is good or too "woke" or whatever. They have entirely missed out on this, and are still doing anxious tribal transactions. Their world is still many things, many peoples, and the focus is only on the small.