> If you have statefulness + mutability then you must do away with concurrency; a different way to avoid the same concurrent overwriting problem mentioned above.

Last time I checked we had plenty of concurrency primitives allowing for that; you might need to wait few tens or hundreds of nanoseconds for a lock (or few orders more over network), but it works just fine

All of them depend on temporarily suspending concurrency in order to synchronize. Even atomic exchange operations are like this at the hardware level.