SAS
No doubt in my mind that nav is poorly addressed in PPL training, but it's not because of over reliance on GPS.
GPS is just about never used in PPL training (fair enough, not in the syllabus) and I would suggest a simple (if impractical) experiment:
Get a 100 PPLs (chosen to be a representative sample of experience of real PPLs) to fly a decent x/c route, through some real airspace issues, e.g. Goodwood to Prestwick. In the winter, in a standard non-deiced aircraft.
Well within their PPL privileges!
Get 50 of them to blindly follow a moving map GPS while remaining at/above the planned MSA and not looking at the ground at all, for the whole route. No chart permitted aboard the aircraft, either.
Get 50 of them to navigate using dead reckoning as they've been taught.
Which group do you think will bust more airspace?
Which group do you think will have more fatal accidents along the way?
I think the answer is obvious.
"We" teach navigation as it was in 1920, with no CAS, and in the days when flying was done by real (generally wealthy) men wearing leather caps and goggles, in cloth covered biplanes, who liked danger, excitement, who got admired by the press and the public for doing wild things (even if 99.9% of the public could not afford to do these things). This favourable situation lasted, in one form or another, till about 40 years ago.
But everything else has changed.
Today's PPLs are pretty average people, and most can't even afford a decent headset.
The training industry, what's left of it given the above rather significant constraint, is keen to strip £8000 off everyone who walks through the door - can't blame them, if I was running a school I'd probably be doing the same.
The CAA (the only organisation with the oversight to do anything about this) isn't bothered. They run safety seminars telling people to not fly into hills - especially not with a GPS.