This sounds like an absolutely horrible experience, I'm so sorry to hear this.
At the same time, aside from the open source programming, which is welcome, I have not ever seen any of the other things you mentioned, but I also took the time to look for a more "quiet", dataviz-oriented server myself. My feed is more people I explicitly follow than local timeline, which makes it a much more curated experience.
Can I ask you what kind of interests you were searching for when deciding on an instance? Because my hunch is that you basically had to deal with a "search engine" kind of problem, but for fediverse instances. I wouldn't be surprised if programming, anime and manga has a ton of "4chan-esque" places that drown out the more quiet "safe spaces" unless you take some time to dig deeper before settling down somewhere.