Many people have argued that RSS is too complex compared to JSON... and to be fair it's clear now that every new API from every service is JSON based. At this point, XML is clearly on the way out for web people!
That's the same kind of attitude that caused the decade of "XML for everything, and damn the technical requirements".
Agreed, and we (superfeedr) have been strong advocates of XML for some problems. We are also tired of hearing: give us JSON or we won't care about RSS.