Censorship, beyond what’s required by law, is doomed to fail.
So you can lose credibility two ways, one by not doing any censorship because people on the internet will be the worst if you let them. Doing too much censorship is also bad because people don't like that either. Of the big causes of censorship currently, I think of things like youtubes copyright claim process and how that is routinely used as a censorship backdoor by anyone - including the police. Sometimes its not even for any good reason and done by unthinking bots. This is banning more perfectly fine content than anything the government has done. I don't understand why there isn't more pushback against that process to punish people for frivolous claims.
If you look at every attempt to create "The Uncensored Free Speech Version Of [ANY_SERVICE]," they all, inevitably turned into a 4chan-like trashfire. You've got to have some kind of moderation.
So whats changed?
Well, I have my thoughts, but one thing is for sure, as soon as the platform itself tried to start moderating, that's when things really started changing.
That’s nostalgia - the BBS world, Usenet, IRC, etc. absolutely had norms and people who violated them were routinely blocked. Where I grew up there were some BBSes run by e.g. evangelical Christians who aggressively restricted the FidoNet channels they carried and the files allowed to be uploaded, and later some of the business-focused ISPs sharply limited things like Usenet (which had its own moderation system). When I ran a FidoNet node, I had to agree to community standards with the boards I peered with because the operators didn’t want to deal with certain types of hassle.
What was different is federation: back in the early online era, someone who was booted off of one system would go somewhere else. The problem with services like Twitter is that they’re centralized and so when people break their terms of service don’t want to go somewhere else, so they complain about censorship when they really mean “free hosting and promotion”.