User blog comment:MisterWoodhouse/Social Activity, the 2010 Editor, and Unpausing Migrations/@comment-39478741-20200924214742/@comment-30551213-20201001033551

It's outdated because it's running an awfully old version of MediaWiki. Go check Special:Version and find that legacy is based off MediaWiki 1.19! This version is five years out of support by the original developers.

Users have been complaining for a long time about this, and it's time to leave this old version behind, IMO. Not saying that UCP was a good way to, but the alternative is far worse.