Of course the technologies still exist, but who is actually using that at scale? Chrome never supported RSS feeds to begin with, Firefox dropped support in 2018 or so. Pingbacks outside of the wordpress dot com ecosystem are disabled by pretty much everyone due to rampant spam.

RSS works at the scale of the individual reader, any other scale is fairly irrelevant. Browser RSS support is fairly irrelevant too; just like there are email clients outside browsers, there are RSS clients outside browsers, and some email clients are also RSS clients. Pingbacks also aren't relevant to usage of RSS by readers.