That's like saying "how is IRC dead today" when Slack/Discord/WhatsApp/Zoom/etc exists or Yahoo style portals when Google exists (yes Yahoo is still a real business) or "how are horses a dead transportation" when cars exist in 1930s America because horses can still walk on roads (aka takes a minimal investment to support).
Sure they still work and will continue to work but let's be honest it's a super niche technology and it didn't survive/flourish because it was flawed and fundamentally nerdy option people stopped caring about.
Supporting RSS takes the bare minimum of effort. Yet even in 2013 (aka a decade ago) RSS was declining in usage before Reader was killed.
I support open platforms but RSS had a super noise-to-signal UX and I personally don't miss it.
Google didn't kill RSS, they killed the best RSS product at the time and accelerated a dying protocol that would still be only used by HN's demographic and little else.