Earlier quoted context omitted.
> - Yes, Mozilla has made missteps with Pocket and Mr. Robot. and the removal of RSS support. So much for the champions of the Free Web!
It was removed because - pretty much nobody was using it; - it's pretty easy to reimplement as an extension. Championing the Free Web is harder if you also need to champion the dead web. edit "nobody" => "pretty much nobody"
You'll need a source for that, since most Wordpress sites which constitute a HUGE part of the web have pretty much by default rss feeds. It's not because you are not using it that nobody is.
And even you premise was true (which is debatable), it cost absolutely nothing for Firefox to keep a functional RSS reader without putting much effort into it (or instead, you know, putting efforts in pushing ads to people who never wanted them).