What do you use instead?

I've been using MobX on a quite large and complex React app for a few years now and I have no regrets. The key, as in all programming, is to make your (observable) state as small as possible. You shouldn't have observables that are derived from other observables; you should have computed values. You should use reactions sparingly and almost never use them to mutate other observables. Etc. MobX lets you treat state as state and then get all the benefits of memoization and reactivity that you want, for free. It only gets hairy when your state itself gets needlessly hairy.

I was not a fan of knockout AT ALL. But here we are.

People would get too clever and abstract way too much. I don’t see the same with Vuex and MobX but I can understand why you feel that way based on this reply.

The concept of having a centralized state / store with complex apps is impossible to ignore IMO (even if you just have plain objects holding them). At that point sprinkling in a pattern to standardize access isn’t that much overhead.

I've been burned by observables in a large scale knockout project too. Definitely left my weary of observables for UI development in general.