After my flying “career” was over I spent a few years in the simulator world, instructing in a state of the art device and I agree with Bob. We never claimed that we could replace flying but we could make each flying hour much more valuable. We could also do things in the sim that simply were not possible in live flying. The choice was often not “shall we do this in the sim or the aircraft” but “shall we do it in the sim or not at all”.
The other problem with the synthetic only route is the physical demands of FJ flying. 5 years or so after my last flight in the jet I was lucky enough to get a pax ride. “This” I thought “will be no problem at all, I instruct in the sim every day, and I’m in the sim cockpit pretty often, I’m all over this” . What a shock! By the time I had all the winter gear on and had clambered into the cockpit I was already suffering. After a fairly benign hour long trip I was wrecked. Traditional simulators cannot reproduce that and even the new centrifuge/ sim at Cranwell only goes some of the way.