User blog comment:MisterWoodhouse/Fandom is upgrading to a modern version of MediaWiki/@comment-33853489-20190620154245/@comment-25252539-20190620154855

That means you get better security, easier editing, more features and tools, less bugs, etc...

Fandom is running on really ancient MediaWiki 1.19  released in 2012 vs their competitor which using MediaWiki 1.31, and what they want is to upgrade to newer major version.