The paramount quality of a good app is how easily it gets out of the way and lets you enjoy the content. Pocket Casts has done a spectacular job at that.
I've been using Antennapod for over a year now and it a great podcast app and does a lot of stuff the paid ones won't even do, including syncing what episodes I've listened to to gpodder.net, searching iTunes and other websites and just having an easy to use, simple UI.
It's just a shame that these FOSS apps which have much lower overheads as well, just can't market themselves as a commercial proprietary application like Pocket Casts can.
For other people there it is; there's the appeal. It does everything they want.
To add to that, there are issues between the GPL and the Apple App Store ToS so open source apps on that platform are at a disadvantage as a result.
When I was using Downcast on iOS refreshing all feeds took ages and a lot of traffic (some feeds with a lot of episodes can be more than 500 kB, that adds up when you're subscribed to 50 feeds) and since the refresh wasn't even threaded all it took was a single slow server to block the whole refresh.
Now in Overcast (which does server-side crawling) the refresh is instant and I can even get immediate notifications about new episodes.
Serverside crawling means your app just needs to grab whatever's different instead of downloading 20 RSS feeds every few minutes/hours. Definitely a bandwidth saver
You mainly seem to rail against people preferring a commercial solution over a FOSS solution. The reason for that is simple, people don't care about the difference and Pocket Casts provides a better user experience that just works instead of having to cobble different parts together yourself.
Also in my experience, relying on small-scale FOSS apps means opening myself to the vagaries of their on/off development cycles, dealing with their underinvestment in design, and the impossibility of them spending significant resources on good old fashioned centralized backends. Of course FOSS apps have many strengths of their own (esp. in the desktop content/code creation category), but the apps on my phone are "lifestyle" - I want them to be rock solid, aesthetically pleasing, to require zero thought, and to respect my privacy, and I'll happily pay good money for that, which is something I think in this day and age should be encouraged. FOSS apps are simply a different value proposition.
That's the issue for me. If it's proprietary, I simply don't trust it to keep my data secure. I have no way of knowing that myself.
And that's the great thing about gpodder too, you can host your own instance of it so you are in total control of your services.