Personally, I don’t care at all since we’ve gotten JSON feeds.

https://en.wikipedia.org/wiki/JSON_Feed

Not every programming language I use can output RSS/Atom/XML by default, but pretty much all of them can output JSON natively, no library needed, just fine. The spec is short and easy to understand, to the point it’s little effort to manipulate the feeds, adding to them or consuming them even without a dedicated reader if need be.

To consume other people’s feeds, I mostly don’t care what format they are as long as my reader can understand them. To generate my feeds, I always use JSON. Most of them are for personal use, but even for those which aren’t, I never had any complaints (most feed readers seem to be able to read those just fine).