FNG
I was hoping my comments would be taken partially tongue in cheek
if you fly from point A on accurate heading X at accurate speed Y for accurately timed minutes Z, checking for errors and drift as you go
Accurate heading needs an accurate wind forecast. Very hard to fly accurately in turbulence especially in certain aircraft types. Doing so for extended periods can be extremely tiring. Checking for errors needs recognisable features down below - trivial sometimes (e.g. in sight of the coast), very hard at other times.
But I appreciate this is an interminable discussion, because one CAN fly anywhere using purely visual nav - if one is good enough at both aircraft control (so enough of your brain is left over for other stuff) and terrain recognition.
But both these skills are lacking in fresh pilots. I suspect that anyone with enough IQ to pass the PPL exams will be aware of their limitations and, maybe just perhaps, this is a factor in why most people pack it in so quickly. There are many places in UK airspace where you really have to know where you are. Some French airspace (e.g. near LFBZ) is even more complicated due to bits of military areas.
I know GPS cannot be brought into the 45-hour PPL which is at best only barely adequate now. For as long as this is the case, whether everyone should be told to fly "WW1-style" or whether the flying scene should be dragged kicking and screaming into the 20th century, will remain an interminable discussion. Until it is too late.