That’s all well and good for the military, but what about the civilian world? It’s more likely that an adversary would try to disrupt civilian air traffic by jamming GPS.
Any radio-based navigation system can be jammed, but if multiple navigations systems are spread over multiple frequency bands, it makes it more difficult to completely shut down air navigation. And I’m not convinced that the VOR MON will leave enough of a backup. Sure, VORs and LORAN aren’t perfect either, but VOR+LORAN would have left a fairly robust backup system to GPS. It also seems like it wouldn’t be too difficult to integrate LORAN and GPS into the same receiver so they can both cross-check each other.
Inertial and celestial navigation are of course naturally resistant to jamming, but they also require every aircraft to be equipped with them. I hope this doesn’t turn into another mandate for GA aircraft.