The app is mainly used for the Discussions, and not all wikis are eligible to be on it.
There's a huge disconnect between the mobile platform and the desktop version. My hope is that this UCP thing will help bridge that gap. I've got users on our wiki that are only on the Fandom app and don't even realize that we're a wiki with information.
UCP is more focused on desktop and behind the scenes upgrades, with a few changes to things like the addition of the mobile editor, but I guess we can hope.
I disagree Noreplyz. While it is true that behind the scenes updates benefit desktop, one of the main motivations is that UCP is more mobile friendly. Most notably the addition of mobile editing.
I think it is important to point out that there are 3 ways to view a wiki:
As Tupka217 already said, only a select few wikis are available via #1. Even then, it is primarily for content viewing and community interaction; not content editing. For legacy wikis, mobile view has a similar lack of editing capabilities; not so for UCP wikis. The layout and function of various features are different in mobile view compared to desktop view. Currently, wikis cannot use CSS/JS to customize/tweak the mobile view. Whatever Fandom's backend decides to show is what get's shown. As such, it is much harder to control how pages appear in mobile view than it is in desktop view.
Now I get it, too bad my favorite wikis probably didn't eligible for it.