As much as I hate Snap and remove it from my Kubuntu systems, I don't see where it is failing. I frankly see a lot more non-linux-focused vendors support to snap than flatpak. Could you expand on that point?
It’s not a question of which one will succeed between snap and flatpak, it’s whether the ecosystem really needs either one of those.
unity failed because they abadoned it, but it was way better than wayland+gnome. the problem was that it was based on gnome2 and had mir under its belt, so it would've been really really hard to somehow upgrade it
Unity didn't fail: ongoing development on it was cancelled because there was no way to successfully monetize it. It was, and remains, one of the most successful desktops out there.
If your definition of community is "people who develop desktop environments for open source software" then you're already limiting the size of your community to a few dozen or so individuals, and we had a few dozen contributors to Unity so I'm not convinced of the strength of this argument.
If your definition of community is "people who don't use Unity" then of course "everybody knows" that's trivially true. Some people also know it's a tautology.
At the end of the day the scorecard reads:
- Mir: failed
- Unity: failed
- Snap: mostly failing
Meanwhile RedHat takes over stuff that doesn't work, makes it work a bit better, and pushes it on the whole ecosystem as "the" solution. And they win, and win, and win.