Design seems to be a work that anyone from the outside can do because the result is considered visual and 'like' subjective, whereas behind good design are disciplines that have been studied for years, such as composition, typography, color theory, and user psychology.
A person who has not trained in graphics or interface design, who has not developed a product from the beginning to the end, often does not even see 'what is wrong'. The resulting work may appear 'not terrible' at first glance; but alignment disorders, inconsistent spaces, and false hierarchy create insecurity in the user without realizing it.
This damage is invisible, so it's dangerous. The user doesn't say 'this design is bad'; it just comes out without filling out the form, doesn't find the product reliable, stops buying it. You live the loss by numbers, but you can't see why.
A designer’s ability should not be judged solely by a degree or years of work. Review how they explain decisions, account for accessibility and prepare deliverables for practical use.