A lot of stuff around granular authorization controls and auditing - there’s a huge gulf in most of the atlassian products between a system admin and project admin and there’s a ton of admin actions that never show up in any audit trails or history within the app.

Also: email handling sucks and support for the scaled agile model is pretty non-existent.

Just in general though, take a look at jira.atlassian.com and see all the issues with thousands of votes that have been unresolved for years and years.