Might or might not be true. But I'd say producing good diagrams is implicitly mandatory if you want to advance your career.

I didn't use them much as an individual contributor, but as a lead, I rely on them all the time to communicate ideas.

PlantUML makes it so easy to do so.

I spend my day trying to convince many developers they should engage in formalized design at all. Big fan of diagrams here.

Same here, with little success. Often people want to find some tool to generate diagrams from the code, which totally misses the point.

Still, I use them in my projects and they help me very much.