I've used Wiki.js for a while but was always annoyed of the loading times. It's just one of those applications that render everything in the client.
So I haven't stopped looking for other applications and when I tried BookStack I knew I found my solution: Loads amazingly fast, while running in the simplest environments as it's PHP.
Previously I have also used DokuWiki, which was also simple but I didn't want to write in Markdown, and especially explain it to others.