Android shouldn't be considered Open Source anymore, since source code is published in batches and only part of the system is open, with more and more apps going behind the Google ecosystem itself.
Maybe it's time for a third large phone OS, whether it comes from China getting fed up with the US and Google's shenanigans (Huawei has HarmonyOS but it's not open) or some "GNU/Linux" touch version that has a serious ecosystem. Especially when more and more apps and services are "mobile-first" or "mobile-only" like banking.
It's been that time for years. But it's easier said than done. The closest we've currently got are the various phone-targeted Linux distros out there. But they're not quite ready for serious usage for me; at least not on the Pinephone. Still, that's where to put your time & money if you're serious about wanting a change.
PPpro was mismanaged especially badly. Nothing against the amazing community- it's just there were some hardware/firmware decisions by pine that made it especially hard to develop for. Meanwhile, the non-pro version is handicapped by a very slow processor.
There's still some development happening, and the window managers like KDE are still improving stuff on the front end. But you're right, it has slowed down. That all said, this is still the only non-Google/Apple device you can get in the USA that actually kinda works. I used both the non-pro and pro versions for a few months a couple years ago as my daily driver. I could make calls, send texts, connect to matrix, etc. I wouldn't claim that "it just worked" but it did work.