And, annoyingly to those who prefer other distros, one major selling point for *ubuntu distros is that nearly every aspect of setup/configuration/adjustment is documented somewhere, be it a blog post, wiki, stack exchange, forum post, etc.

For certain less popular desktop distros (e.g. slackware, arch, and to a certain extent fedora, debian, etc.) there are lots of little things where you find some decent documentation, but you have to know how to adapt it to your particular OS version. Things like that kill a beginner's curiosity, because in the beginning, you just want to get some random thing working, not debug linux kernel versions and package repositories!

Definitely agree! Ubuntu have tons of support all over internet. Virtually any problem has been already solved by someone on the internet which is incredible if you are beginner. As for lightweight version of Ubuntu I would recommend Ubuntu Mate.