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.
It would also be kind of weird to compare to Arch, since Arch makes you configure so much yourself.
Like, my biggest complaint is that I feel extremely naked without automatic btrfs snapshots. Obviously, you could configure those on Arch, but that would require understanding significantly more about btrfs than I currently do.
I had to read up on it just now, but I don't think, that works in my case.
So, the worse distro here is Kubuntu. Personally, I use openSUSE Tumbleweed.
My problems with Kubuntu are mainly:
The bundled KDE is out of date and unstable. KDE is integral to my workflow.
No automatic filesystem snapshotting. If I fuck up, that's my system ruined.
And yeah, it seems like Distrobox is mainly useful for running CLI programs, maybe individual GUI apps, but not whole desktop environments. And it re-uses the filesystem of the host system, so that kind of precludes filesystem snapshots, too.