MobX is how you get spaghetti code and state changes everywhere. That is why we (our company) moved away from the observer pattern that MobX and RxJS use.
I've seen plenty of spaghetti code with just about every other React state management (reactivity) approach. The benefit of MobX to me is I can write a more traditional "domain" layer and wire the view in on top of it keeping a good separation between business/domain logic and UI concerns.
