"Carbon capture research" has been an excuse to divert funding away from renewables for 20+ years. It's hardly made a dent in emissions and it's unlikely to change any time soon.
I've come across some old time r/fatpeoplehate people and they pine for the olden days when they could freely say what they wanted about fat people. They aren't signing up for any reddit alternatives any more than anyone else is.
The hardcore haters, trolls and extremists will find other platforms, but the majority of toxic users are passive readers, or occasional commenters who randomly stumble upon subreddits, and aren't going to dedicate themselves to another platform.
In my experience with Firefox devs, if it's not important enough to fix immediately, bugs will simply be closed and ignored. I've come across other bugs that exist for 10 years (not security related) which were closed again each time they were brought up every few years.