I wonder if that has anything to do with the popularity of subs that are about disliking things or groups of people. That kind of shit drives engagement but turns communities toxic really fast.
I use(d) RIF, which let me filter subs out of my feed and the experience has been a lot less horrid, except for when those subs leak their toxic waste into other discussions, which happens way to often.
One UI change that could address this somewhat would be that if multiple communities post the same link, the discussions are grouped together in an expandable box on the main page. That wouldn’t require any voodoo magic to merge the threads, and it would make room on the main page for things other than news about reddit.