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.
Each one has good parts, but I think openSUSE did a lot to make things easier for new users to linux
Install, you see software summary, you can click and alter what patterns or packages you want included.
auto snapshots when you enter package manager or admin tools, easy rollback with snapper or boot list
a GTK front for all of YAST2-GUI components. All system, network, firewall, service, packages, boot and kernel config are available as GUI dialogs (as well as many others)