They are called "user" interface and "user" experience, after all. Any "user" can call it bad and it can be a valid point. It can also definitely be valuable in

They are called "user" interface and "user" experience, after all. Any "user" can call it bad and it can be a valid point. It can also definitely be valuable input. But an engineer identifying a design flaw in a bridge or an English major identifying errors in language use are people that have specifically studied those things and have a depth and breadth of knowledge that most "users" don't. Programmers aren't UI/UX experts just because they use applications.