The person writing this must have little to no experience developing UIs in classic frameworks. React has warts, but it is a decent implementation of reactive U

The person writing this must have little to no experience developing UIs in classic frameworks. React has warts, but it is a decent implementation of reactive UI, given the constraints of the web platform. Of course you can achieve a speedup doing better what React does with less context - updating only the exact parts of the DOM that need updating. You will pay the price in terms of code complexity. As for asynchronous behavior, this is not something you can avoid. You can not block on network requests, or block until the user clicked somewhere. React does not push you towards async any more than the platform does.