The fundamental thing that the Atom creators didn’t understand (and that the Atom supporters still don’t understand), is that Atom isn’t somehow separate from RSS. There’s this idea that RSS fractured, and that somehow Atom fixes that problem. But it doesn’t. Atom is just another RSS splinter. A new name doesn’t change the fact that it’s just one more standard competing to do the same job, a job for which any of the competing standards are sufficient.
No one outside a fairly small group of people care at all which standard is used. They just want it to work. Atom, RSS 2.0, RSS 1.0, RSS 401(k), whatever. As long as it works, the users are happy. The RSS “brand” very much defines the entire feed category, though, so on the rare occasion that someone does know enough to choose, they will tend to choose RSS, because it’s got “the name.” They will also tend to choose RSS 2.0, because it’s got the bigger number.
RSS, and especially RSS 2.0, are very much entrenched in the feed “industry.” Atom hasn’t taken off because it doesn’t bring much except a new name. Why switch away from RSS when it works just fine? And why even bother using Atom on new projects if RSS is sufficient? Switching to a new feed format mostly means extra time spent learning the new format.
If nothing else Apple’s exclusive use of RSS 2.0 for podcasts means that RSS 2.0 is here for the foreseeable future.