In 2020 Fandom/Wikia started a move to overhaul its software to base it on MediaWiki 1.33. Wikis using SMW were to be among the last to be switched; still waiting in early December 2020, while a popup at the top of most pages warned of the change and gave a link as below.
Read explanations and a summary of progress at https://community.fandom.com/wiki/User_blog:MisterWoodhouse/The_first_migrations_to_the_Unified_Community_Platform - in early December 2020 part of it said while listing features that would delay switching: "Semantic MediaWiki - Soon to be deployed!"
Detailed updates may be at "Technical Updates" - https://community.fandom.com/f?catId=3871017659269122999&sort=latest - where the "November 20" one said "... we are starting to switch gears from UCP migrations (set to finish in the next month+) to the unified experience work. ...". That "+" could mean anything.