UI/UX contractors are not much better - they still need to justify their billable hours somehow, leading to pointless changes.

What's really needed is internal pushback against UI changes without user studies to back them up as well as a willingness to listen to user complaints and not just brush them off as "people complain no matter what change is make hurdurdur". Perhaps also an understanding that even neutral changes (as far as usability is concerned) have a negative cost to users.