Maybe the workflows, etc., are inherent complexity, so that any similarly-flexible product will have the same problems.

But the awful client-server architecture, where anything you do takes several seconds of waiting for the client to send who-knows-what to the server and get data back, even selecting something from a dropdown... that is absolutely just Jira. A competing product would be able to deliver much, MUCH snappier UX. Jira is just the crappiest, slowest UI that I have ever had the displeasure of being forced to work with.