If people who currently call themselves graphic designer rebrand themselves as graphic artists, it seems likely that they will lose jobs. A big part of the reason that people want to be called designers is that designers get paid more than artists. Like you said, design is more respected (at least economically speaking) than art.
Design also plays a fundamentally different role in modern digital settings than in traditional ones such as poster design. Designing a great UI involves psychology, engineering, and fundamental truths about human behaviour. A mediocre designer might think that making something that looks good is all that matters. It’s also possible to build metrics for evaluating the efficacy of a digital design into the design itself.
Design is about function, and in situations where the function of something is to be aesthetically pleasing it makes perfect sense to prioritize aesthetic values. There are also certain things, like movie posters for example, where quantifying its effect on function is nigh impossible. You can’t exactly track how many people looked at a poster on the wall and then how many of those people went on to buy tickets. Is the person who created the poster limited to being called an artist because of the unquantifiable nature of their work?
Many of the examples you gave are examples of this. Stage design, sound design, and motion design all serve the purpose of providing a memorable/or pleasing aesthetic experience. A play’s set functions as a character and if the designer makes the wrong choices, the proper feeling will not be conveyed. That is a bad design. The playstation intro was designed to be a memorable part of playstation’s branding. Motion design can make something feel safe and calm or dangerous and energetic. Most of these things also lack the feedback mechanisms that you say are required for something to be considered design. The only feedback on a badly designed stage after it’s released to the public is a review in the local paper. Stage designers do go through repeated iterations and try different ideas before opening night, but there isn’t the level of direct user feedback you seem to want.
It essentially seems like you are making a semantic argument to elevate people with technical knowledge over those without it.
I think it might be more useful to draw a distinction between graphic design and digital design instead of drawing the line between graphic design and graphic art. There are fundamentally different needs and variables in print design as opposed to digital design.
All this being said, I do agree that people who don’t understand the scientific aspects of UX/UI design should not call themselves designers. Anyone with adobe illustrator can make an aesthetically pleasing button or icon, but it takes real thought and repeated testing to incorporate the button into a UI that provides the desired experience.