There’s also the complexity of approach procedures that they need to follow in order to mitigate noise complaints. Back in the old days, they’d just fly from radio beacon to radio beacon, with look-out-the-window navigation for the final approach.
These days, lots of airports are within or close to cities, which means a much more complex routing and specific altitude and speed restrictions. GPS made that possible; they’re simply too much workload for pilots.
So yeah, in emergency situations where GPS fails completely, there’s going to be some changes to procedures needed in order to make that work. They’d also need to increase separation between planes in order to prevent problems.
The simple solution is: nobody should fuck around with GPS since we literally all benefit from it.