Which is why sketch UML is popular. It looks like UML if you squint and gets the important reasons to use UML on a whiteboard. Then after everyone agrees you erase the whiteboard.
Sure, but you also take notes of the features, constraints, and invariants that were discussed. At the end of the meeting, instead of having a diagram which acts as a rigid spec, you have a set of notes and diagrams which informally describe the problem space, the proposed solutions, the benefits, the drawbacks, and any important details. And that's more useful and more flexible than UML.