For example, I'm using Debian, and I think we could learn a thing or two from Mint about how to make it "friendlier" for new users. I often see Mint recommended to new users, but rarely Debian, which has a goal to be "the universal operating system".
I also think we could learn website design from.. looks at notes ..everyone else.
Fedora's installer is abysmal. There's a number of installers it could learn from. They're working on one at the moment, so I hope it's good.
Enabling access to proprietary software should also install audio/video codecs. Or at least have a separate checkbox for it, like (I believe) Ubuntu has.
Calamares has poor integration with the rest of the ecosystem including their existing tooling. For example, it has no kickstart support, and no support for their immutable installs (afaik, anyway). It was less effort to put their existing cockpit tooling into anaconda and make a whole new web ui than it would be to add support for all their stuff into calamares.
The installer is the single one reason I can't switch to fedora. I have several drives in my machine and I like to separate them, but their installer scares the shit out of me. I can pull it off for sure, but I just don't want to take the risk