First of all, there is the problem of senior editors being in control and if you do anything, they just revert it, or delete it. There are reasons why there are already many different wikis and not just one.

Then as the other commenter shared, they have the goal of a neutral point of view, but that’s an idealistic goal that can’t be reached. The neutrality with which something is presented is sometimes a problem. For example in political spheres it can make more sense to read two very biased articles from opposing sides, than one that tries to present both sides objectively.

So it would be really helpful to see side by side comparisons or disambiguation pages that lead to different perspectives.

And you can sort of do this already, but the point of federation is also that it’s more tightly integrated than “you can have your own forum” which was true before as well.