React Query (and other query caching libraries) are great until you have overlapping data between your queries. E.g. you edit a message in one place but other queries that show that same message (like a preview in your chat list) don't update.

Having a complete query engine on the client makes this a lot easier to deal with. It's why most popular messaging apps will use SQLite on the client to render the UI and build their own sync engine to keep it up to date with the backend.

That is not a CRDT level solution though, it doesn't work with multiple clients with disparate conflicting data.