It has an incredible amount of flexibility and customizability. PMs take that flexibility and turn it into a draconian list of requirements for tickets and workflows.
PMs want a million ways to extract and analyze information from tickets so they can create a hundred dashboards. The software engineers want simplicity so they can just quickly find what needs to be done, do it, and mark it as done.
Jira can be simple and easy. It's the PMs that turn it into a nightmare, but the hate gets targeted at Jira.