User blog comment:MisterWoodhouse/Social Activity, the 2010 Editor, and Unpausing Migrations/@comment-25494237-20201013101955/@comment-38743559-20201031053834

Because it requires a lot of effort to port changes from New MediaWiki to their custom version. As they add more custom features it becomes more difficult. This means things like security Fixes become more difficult to implement and features that modern MediaWiki has that they want to port to their older version become more difficult to port overall. It is buggy and awful now, but please try to offer constructive criticism. This first step had to happen, the best way to find bugs and edge-cases is to release it out into the wild.