It depends on your use case. The simplest and oldest wiki might be Docuwiki. There is no database, and organization is based on text files in folders. You can make decent wikis with it, but it’s minimalist and can be hard for the users to use it.
Then we have enterprise solutions for collaboration by Microsoft, Google, Atlassian, etc. They can’t be used in our workplace, due to organization policy.
I went with Bookstack for a wiki to be used by a group of people. The interface and fonts are pretty, it’s super fast, installation is easy, and automatic updates have been problem free so far. The content must be organized in terms of shelves/books/chapters/pages, but some people want any number of categories and titles. It doesn’t allow a lot of customization, but the choices made are OK.
Mediawiki is complex, and takes more time to administer. It could make sense for large number of users. I stopped using it after upgrades broke the installation a few times, and, frankly, the interface looks outdated to me in most themes, and needs customization which takes time. Obviously, it’s very customizable, there are tons of resources and we know it can scale to billions of people!