Good point. It's much more flexible and modular to have individual declarations of use cases. Otherwise you quite often you end up with interface segratation principle. This is because you will find that almost all use cases should be able to be used individual. When you need 3-4 in a bundle for a screen, you can compose it in a more local structure and request it on init for example.

But yes, having them individually makes them like lego blocks.

When it's time to implement, you can have a services that implements a set of them, especially related use cases. Or sometimes still individually.

In the past I used to have CRUD interfaces like Services/Managers and creates multiple problems.