I would say browser makers are more at blame here. They never really implemented features to discover feeds so it was always up to the webmaster to include some "what are feeds and how to subscribe" pages. Those are mostly gone now, though the feeds often are still there, just hard to find.

If we want them to become more popular, we just need to tell people about them. But then again, I always struggled to make many of my friends and family - even many other techies - understand what they were and why they are great.

Still, they are around and indispensable or many power users.