How exactly do you update the github of a flathub package with no one actively maintaining it? Not sarcastic. That is an actual question.
And I’m not worried about big officially supported apps. A better example of the kind of thing I’m talking about is older open source games. Flatpak could be great for games. No distro out there is maintaining a current version of every open source game that has ever been released, but Flathub can, and it could be great. Unfortunately anything that’s not being actively maintained is rapidly going to become a 200MB download that whines about security every time you update your flatpaks, even if it doesn’t connect to the internet at all. Even if it’s possible for any random person to update it, who will?
Of course, this doesn’t just have to be about games. There are lots of open source programs out there that just kind of get completed and abandoned. And that’s not even bringing up all the closed source software on flathub that definitely won’t be updated eventually. These aren’t unsolvable problems, of course, but I don’t even think anybody working on flatpak even cares.