I have a very specific complaint: the ease which all sorts of custom fields can be added for _everyone_. Sales will want to add a field to hold their contract status. Lo and behold, engineering now has it. It can be done in the proper way, but it seems that doing it at a global level is easier since that's how multiple Jira installations at multiple companies were configured.
All I want is a ticket, with a title, description, assignee, the current status, an easy way to transition, and comments. That's it. Let my project _opt out_ of any global customization if making global stuff is unavoidable.
Also, the newest Jira UX is... terrible. Tickets should not be THAT easy to edit. How often do we want to change a ticket's description, or title? I'd say, not often. If we do, there's really no harm in having an "edit" button. Old Jira versions had one.