Something that Twitter actually did pretty well pre-Musk was compartmentalisation; Twitter had many different worlds, and if you stuck to one of them, you were often only, at most, dimly aware of the others. This was enforced initially by the basic setup (linear timeline, you see what your followers post and later retweet) and then later, The Algorithm(TM) was pretty good at enforcing it.
Musk came in and almost immediately broke this (it started to fray badly even before the blueticks got bumped to the top of replies and all that). People started complaining that there was porn on twitter now; there had _always_ been vast quantities of porn on Twitter, but in general if you didn't follow it the algorithm wouldn't show you it. I started using Twitter in 2007, I tweeted my last in December 2022. And in the last month or so I blocked more people than in the previous 15 years. I had to block Musk himself then; I find him intensely irritating, but previously the algorithm had never, or at least almost never, shoved him in my face, presumably because the people I followed and interacted with were not Musk People. In the last month, I saw him (and others of his ilk; Jason Calacanis, for instance, who I had completely forgotten even existed) constantly. Along with loads of sports stuff, for some reason; not for me, but I assume someone in the new guard thought it'd sell ads.
Twitter was hundreds of subcultures existing a hairs breadth away, but only barely noticing each other when they brushed up against each other. There were the Nazis, the knitters, the politicians, the pornographers, the scientists, the shitposters... I'm not sure that Facebook will be able to recreate that on Threads, or even particularly want to recreate it on Threads (Facebook probably doesn't _want_ a million porn accounts). It's arguably a historical oddity; the self-segregation originally existed because of the nature of pre-algorithmic Twitter, and when The Algorithm arrived, Twitter was presumably careful not to make it a big change, not to upset things too much. Twitter was all things to all people, Mastodon is many things to a few people, Threads will likely be a lot of things to most people.