I purposefully avoid Vuex until a) the state becomes large or b) deeply nested objects (which reacitivity handles poorly, as whole trees rerender) or c) when I have lots of deep nested Components with a maze of events.

This is where I've found Vuex is a life saver for reducing complexity, organizing state in a seperate area, and having a consistent interface for accessing/mutating data without a tangled web of events and functions across multiple files/layers.