Guild Roster Manager (GRM) is pretty much the only guild management addon that works properly (that I can find at least) but it looks pretty outdated, a skin for it would be amazing!

The default skin for this add-on is too resource-intensive to maintain natively; closing the issue.

AddonSkins's GRM skin has been updated recently, you can try it.
WindTools will soon ship extra polish that automatically reskinning some AddonSkins components when it’s loaded.