I would say it's not rare at all. I collect a long list of RSS feeds too, and a lot of the time to figure out if there's an RSS feed, I have to install on an external plug-in, leave the site that I'm on and do a Google search to see if that same site has RSS, only to find it from an old tweet from 7 years ago, or an outdated web page that has links to RSS that amazingly still work. Or sometimes I view source and search for.rss or.xml. So the emphasis, visibility and discoverability has cratered. And the trend has been towards removing rather than adding.

It used to be a standard to have the RSS icon side by side with the Twitter and Facebook icons, but in the present day that tends not to happen.

Twitter itself used to have RSS feeds, Google News used to have RSS feeds, Craigslist used to, those are all gone to my knowledge. RSS tools used to be native to browsers, and now there are numerous RSS tools out there to manually build feeds to make up for the lack of feeds on sites where people want them. Magazines in particular sometimes don't have them, such as Vogue magazine. And you can look at the prevalence of searches for RSS feeds by users and see in trends over time that people are searching for RSS less frequently.