A good tool needs to be automatically generated from code which makes me think it needs to be integrated in a framework. Or the code needs to be written in a way that is easily visualizable in the first place.
Code comments seem to be the only way to add structure while ensuring the diagrams are kept up to date.
I think there is room for future frameworks that are built with visualization and it’s necessary tooling as a first class priority. When have you ever seen a framework claim it is easy to visualize and understand? Existing software is too much of a mess.