The general mechanism for free software to be developed is for the individual users to make modifications. Not all of them, of course, but the ones who know how to. Someone sees something wrong, fixes it.
Apple interferes with this. If you don't like an app on your iPhone, even if it's open source, you can't just make a minor change because for that you have to pay $100/year and buy a Mac and all of this friction that discourages people from doing it. And then upstream doesn't get the little change (times a thousand individual users with an itch to scratch), and the one-time contributor doesn't become a repeat contributor either.
Not only that, you can't distribute a half-finished app to the public -- even if it's free -- because it wouldn't pass review. But then you can't get any users who might help you to finish it. So the state of open source software on the iPhone is a shambles, because Apple neutered the primary mechanism for free-as-in-speech software to become any good on their platform.
Compare this to Linux on a PC where simple things are about as likely to "just work" as they are on a Mac, more likely to do so than on Windows, and weird and complicated things work better than on either of them because even though they're not always easy they're very nearly always possible.
Which is the perpetual sham of "it just works". Simple things are simple everywhere because they're common and well-supported. Complicated things are often difficult, but some platforms make them prohibitively difficult or simply disallowed, and people confuse this with "easy" because you don't remember spending time to make something work when you can't. But that's not actually an advantage, because you're not obligated to spend time on something that doesn't immediately work, but the option to choose to is valuable when sometimes it's worth it.
