Just to throw my hat in the ring here:
My co-founder and I have been building a hosted version of this[1] for the last two years, because we recognized that while self-hosted wikis work great for techie people, there are a lot of other people who that label doesn't fit.
So we've been working to create a collaborative knowledge-base platform built around some key concepts:
1. Built around cards rather than documents, which allows for a lot of interesting and flexible features. Such as...
2. Granular sharing – on Supernotes, you can share an entire collection of cards, or you can share one card at a time. We also have recently introduced[2] a "friends" features that allows you to quickly drag-and-drop cards onto your friends to share with them.
3. Multi-parent nesting – there is no folder-style filesystem on Supernotes, we allow you to nest cards inside of each other. On top of this, we allow for this nesting to be multi-parent, so different users can fit the same cards into their own unique structure (effectively a collaborative / personalized version of symbolic links).
4. Public vs. private tags – cards can be tagged with public tags that everyone sees, but can also be tagged privately with only tags that you can see. This same idea is reflected across the platform, where we want the underlying content to be the same for everyone but want to allow users to personalize the metadata/structure to suit their own workflow.
5. Focus on speed – we have spent a lot of time making Supernotes speedy quick, and try to make it faster every time we release a new feature.
Anyway that is the rough idea. The goal of Supernotes is to be a sort of data-layer where you can keep all these compartmentalized pieces of content (as cards) and then mix-and-match at will to create very simple or very complex stores of knowledge. We also want you to be able to embed these pieces of content elsewhere (say in a Notion document or on your blog) with as little effort as possible (not quite there yet, but will be soon).
[1] https://supernotes.app/
[2] https://supernotes.app/changelog