There are also a handful of essentially CDNs that host the .mp3 files themselves, but these are more or less completely interchangable. They're just infrastructure for hosting files.
The only player in town that seems to really make a dent in the openness is Spotify which have been aggressively buying out podcast teams and taking them off the open web, and that's one of the prime reasons I cancelled my subscriptions.
Then there's smaller losses like the BBC4 which made most of their podcasts have a 1 month delay vis-a-vis their own app. I have no interest in that. In effect, this just served to curb some of my compulsive newsy consumption. If something isn't important enough to still be heard a month later, maybe I didn't need to hear it in the first place.
Anyhow, I very much agree with the article and I'm happy someone made the point so much more eloquently than I've managed in my many debates about the matter.
But thanks for posting this! Occasionally, I can't find a particular podcast on my preferred site.