When I log in, it shows me a shit ton of articles that I have no interest in. It's like a Facebook feed, or something, where every document everyone in my (1,000+ people) org has written in the last 24 hours is sorted reverse-chronologically. Since I only need to interface with about 10 people normally, this is worse than useless. It actually make finding stuff harder.
But never mind that, how do I find just what I've written? Somewhere there's a list of "recently worked on" things, and that's sometimes useful, but I usually need to edit something I haven't touched in months. I end up having to search all of our Confluence instead of just being able to search only my own articles. It often brings up completely unrelated things and I have to do more work to figure out which are relevant.
When editing, their editor steals OS keys that are used for every app, like Cmd-F for find. Instead of bringing up Safari's find panel, which is 100% always what I want, it brings up their own home-grown find that doesn't actually search the entire page. It only searches the text I'm editing and often does a poor job of it. Other command-keys are also highjacked meaning I can't do normal things like create a new window when editing text. It's bonkers bad.
The calendar section becomes unusable once you have more than about 3 people adding stuff to it. The list goes on and on. I'm actually shocked that anyone here is defending it.