I guess the "easy to reason about" thing people keep saying is meant to tell you that the modern frameworks allow modularization.

Personally, I do find their style of modularization abhorrent. As you said, it's full of boilerplate, it's also full of dependencies, and the worst sin in a software architecture: they don't enable you to specify a simple interface between modules. But they do solve the lack of structure you get when all the code talks to each other freely through the DOM.