An a time when news from quality alternative sources is vital to many people, given all that's happening around our world, the M@M's (Morons@Mozilla) decided some time ago, citing development costs verses engagement, that it was a stellar idea to remove the ability to handle RSS/news feeds.
It's no secret that the woke jackasses at Mozilla corporate are on a mission of "shaping the future of the web for the public good" which translates to controlling what information people have have access to through studies and initiatives.
Contrary to the stated reason of development costs, i suspect that the motive behind removing feed processing from Firefox was to drive people to "trusted" corporate sources and away from independent investigative journalists and analysts who are actually publishing high quality content.
In that vein, there have been several developers who have produced add-ons in order to restore news feed functionality to Firefox, among them, Smart RSS Reader, which happens to be my favorite and which includes feed detection and a news reader. While the feed detection capability of Smart RSS Reader is probably fine for most people, it won't always work for websites that don't publish their feeds, such as YouTube, Bitchute, Odysee, etc., and this is where the List Feeds add-on (GitHub), which allows you to define custom feed detection rules, comes in handy.
If you're looking for websites to add to your collection, check out the Alternative Information Directory. Also see my article, How to access RSS feeds for websites that don't advertise one.
I am of the persuasion that it was originally removed for marketing and advertising interests, only to later be found as a convenient development in the eyes of information controllers. If it hadn’t happened years ago with the advertisers, it would certainly have been removed as the behest of ‘experts’ and ‘fact checkers’.