It’s when people confuse User Experience Design, which is a systemic and architectural discipline, with UI Art, which is an aesthetic discipline. If you have someone who is professionally the latter doing the former job, you get things people think look good but don’t work well.

This isn’t even to knock either: UI artists are essential to making a UI understandable and enjoyable. But people think the skill sets are the same, and they aren’t.

Disclaimer: am a UX Designer.

Outside of big tech I’ve never met a UX designer who wasn’t just a graphic designer. Not a single one.