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.
I use Debian but still use the Arch wiki quite often. It’s a great resource. I improve Debian’s wiki where I can (eg I wrote a few sections on this page: https://wiki.debian.org/NFSServerSetup) but it’s just not the same.