You can easily ignore the vitriol and fake news on Reddit, you can not get around a lot of commercial detritus anywhere else anymore
Huh? I don't follow here: having multiple subreddits is exactly what makes the site usable for so many utterly different niche topics. There's probably a subreddit for repairing 1967 Camaros; do you really want to see posts like that every day in your news feed? I don't. Reddit isn't meant to just focus on tech topics like this site; it's meant to be a site with discussion forums for every topic imaginable, and there's no practical way to do that without subreddits.
Any attempt at pinpointing the enshittification is bound to be extremely subjective. What is clear is that it has been a continuous decline for a long time.
I guess the mobile app was what really broke the camels back but the quality of the posts had been on a downward trend in a severe way since at least Obama's second term, when I think both political parties recognized it as important and began to manipulate it. This is made easier by the partitioning of the site into subreddits. I hopefully don't have to explain here why that makes automated sockpuppeting much more effective and easier to accomplish. It's a fundamental design flaw (if we were to assume the design of Reddit was intended at all to provide a space for authentic personal takes on real issues and by real humans).
There is a danger of the same thing happening to HackerNews but I hope the lack of financial incentives to allow that sort of thing does some work to mitigate it, along with the lack of partitioning of the community.