I still use rss too (switched to using a self-hosted tt-rss after trying out a ton of Google Reader alternatives). I love RSS and mourn the fact that it's not more popular. The main problem with RSS becoming so niche is that lots of blogs/etc. no longer support RSS (I guess I need to look into one of those mailing list -> RSS things).
If the website is still accessible, it's possible to generate an RSS feed using the main page URL. I work on a project called Feed Creator that does this. You give it the page URL and the item selectors: http://createfeed.fivefilters.org/
The most popular newsletter services do make them, though -- blah.substack.com/feed , for instance (don't remember Revue's or Buttondown's off the top of my head)
