UML sucks because it takes forever and if your software changes you have to change your UML. I just use tooling that allows me to generate diagrams on the fly based on the existing code.
In the planning phases I just use Draw.io, but that always ends up out of date and irrelevant once the system actually exist.
I find this kind of comment ironic (your not the only one to make it), its this kind of thinking which lead to UML becoming a complex over detailed beast, rather than be a tool to consistently model intentions.
If you model at the correct level of detail, you don't have pain keeping them in sync, one you start to model the implementation details you need to adding more complexity to your model to be able to sync the model :)
In the planning phases I just use Draw.io, but that always ends up out of date and irrelevant once the system actually exist.