https://gerrit.wikimedia.org/r/#/c/25170/ is a MediaWiki change that's under discussion right now; it would completely remove all core skins other than Monobook, Modern, CologneBlue & Vector. I thought you might be interested in reading or weighing in on this discussion. Anyone with Developer Access can comment in Gerrit -- for an account, just ask at https://www.mediawiki.org/wiki/Developer_access .
Some more resources to look at, linked in the Gerrit comments:
https://www.mediawiki.org/wiki/New_skins_system
https://en.wikipedia.org/wiki/Wikipedia:Database_reports/User_preferences#Sk...
https://www.mediawiki.org/wiki/User:Dantman/Skinning_system/Skin_examination
Sometimes we have to shed some backwards compatibility. And it sounds like removing support for these particular skins will enable us to innovate and move faster. But it's a good idea to publicize this sort of thing so legacy skin users can say "I'll maintain the legacy support because I love this skin so much!", or prepare to reskin, or find some new third way. :-)
Also, thanks to MatmaRex who has taken this opportunity to refactor the CologneBlue skin.