I don't like Fandom as a commercial platform any more than you do, but in-universe topics for niche fandoms simply don't belong on Wikipedia; they would make it harder for editors to focus copyediting time on articles that matter far more to most people.
There are nonprofit wiki farm alternatives to Fandom that are a better solution to that problem.
But if they stop keep deleting “niche” content from Wikipedia, then people won’t have to use Fandom instead.
You know, the commercial, ad infested wiki that was also founded by a Wikipedia co-founder.
I don't like Fandom as a commercial platform any more than you do, but in-universe topics for niche fandoms simply don't belong on Wikipedia; they would make it harder for editors to focus copyediting time on articles that matter far more to most people.
There are nonprofit wiki farm alternatives to Fandom that are a better solution to that problem.