Instrument failures are rare and might impact a handful of aircraft; GPS jamming impacts every aircraft in the vicinity. ATC might have capacity to plan low fuel-consumption flight heading paths for a small number of aircraft, but not 100%?
ATC / radio failures happen. If ATC can't plan a route for you, you're still the pilot in command and responsible for finding a diversion airport and getting down safely, and for having had enough fuel to deal with traffic while doing so.
Sure -- I don't think the concern is literally falling out of the sky, so much as having to divert to another airport that isn't being jammed (inconvenient). But we're speculating on the basis of a vague complaint.
