I’ve never been a fan of Use Case Diagrams. I always thought they were an example of forcing information into diagram form that is better captured in a simpler structure, just because someone thinks diagrams are always easier to understand. Or because the folks behind UML thought they had to have a diagram for every possible need, no matter that putting some information in diagram form actually makes some things harder to understand.
For systems with lots of functionality and dependent use cases, a Use Case Diagram can be practically un-usable. Especially once you start having a lot of <<Extends>> and <<Includes>> in the diagram. Luckily, most of the Use Case Diagrams I have seen don’t have many actual use cases in them, and have few or no <<Extends>> or <<Includes>>. For the simple systems, a Use Case Diagram isn’t that bad.
But in the end, I think they are a bit of overkill when you balance the usefulness of the results versus the amount of effort. You need diagramming software of some sort at a minimum, and I think there are simpler options.