UML is a tool, nothing more, and whether it is useful or even crucial depends solely on your development and design workflow. There are many ways to Rome, and some of them involve UML, while others don't.

If your workflow relies on UML to document or plan your architecture, then dropping it would be silly. If UML is the best possible way of communicating the project structure to other team members (in the wider sense), then by all means, use it. But if the project works fine without UML, then making UML diagrams just for the sake of it is nonsense.