Fandom (I really prefer their old name, "Wikia") is a great concept. Deal with hosting the wiki so you can focus on content. The problem is that they need to make money, and to do that, they do it with some of the most obnoxious ads on any reputable site on the modern internet. Using their site on a mobile browser is one of the worst web experiences I've ever had. Autoplaying video ad banners on the top with a smaller ad banner on the bottom while I scroll past an ad in the middle of the article.

I'm all for seeing wikis leave them because it'll be a huge usability win. Fandom can still fill the gap for small niche wikis that don't want to deal with hosting and such, but larger established wikis using their own platform will be great.