User blog comment:MisterWoodhouse/The first migrations to the Unified Community Platform/@comment-44421716-20201206151116/@comment-1038387-20201207062635

"I don't like it" and "I prefer the old one" are not things that can be acted upon. Editor performance is being worked on, but these are the standard editors and you're going to have to get used to it - the old editor is no longer supported so can't come back.

Insights was just a portal into Special:SpecialPages. Those have always been there and are still there. It was a custom module they thought they didn't need anymore.