I mostly agree, but I would qualify this with saying you don't need to know exact UML. I wouldn't worry about filled in triangles vs. diamonds, just the big ideas.

Like everything enterprise, before it UML was wrapped in a three ring binder and sold by consultants it was created to solve a problem. That problem is; at the beginning of a project(or at cross-team-collaboration-bs-meetings) you'll have an idea in you head, a fist full of markers, and an empty whiteboard. How do you go about explaining that idea to everyone in the room? UML was an attempt at standardizing some of the boxes-with-lines schemes everyone invented.