Fragmentation comes with open source. State management is fragmented on the backend as well: PostgreSQL, MongoDB, Kafka, Redis, Dynamo, Influx, etc...it's just that state management fundamentally has different trade-offs based on how you structure it (and may involve 1 or several of these).

If your app is simple, you don't really need a separate state-management solution (just use the built-in React useState and useReducer hooks). If it's complex, you have a choice to make, but that's a fundamental issue with apps at scale and you have to make those choices top to bottom.