All the "Software Engineering" classes at university were just UML. Many years I thought SE was just that, UML.
When I did my first job interview I was rather relieved that the hiring manager wanted me to draw UML. He was very pleased with my UML skills, but he always said, I shouldn't draw it with all the details, just the basics are enough :D
That was 2011... I never had to use UML in an interview again. But I often used it as a documentation tool for a big PHP codebase, I had to manage.
UML and ER diagrams are often an overkill when designing an app. But they are nice to visualize what is going on in legacy stuff.