You can see it in DS9 and Voyager, though some of that is down to the death of Roddenberry himself as well no doubt. The shows closest to showing a communist future suddenly decided to get dark (whereas other more capitalist aligned shows were all sunshine thinking that the world was good and safe now), to insert fiat currency, gambling, etc prominently. It became unthinkable and too far-fetched to consider a better world, suddenly Star Fleet is being drawn to reflect American propaganda about the USSR, secret groups within it acting outright maliciously, crushing dissent, oppressing people, doing murderous conspiracies as part of an official secret “section” (secret police you might say) rather than say a group of bad people operating without official sanction and going rogue as happened in a TNG movie. Contrast to ToS where the problem was essentially ignorant or pompous commissar stand-ins throwing their weight around without understanding things “in the field” as Kirk did. You even have anti-state groups in the maquis who show up in DS9 to push the agenda that this communist galactic government is in fact so bad that there are those willing to rise up against it and be seen as heroes, something continued to a degree in Voy.