Is some of this resistance to the loss of ADF just nostalgia?
I think this is the correct question - in other words do we need the ADF.
Practically, so far as GA and en route navigation is concerned the answer has to be no, because GPS has replaced the ADF even if VORs are being used with GPS filling in the gaps between low level reception.
However legally, and particulaly in so far as let downs are concerned, the situation is more complex.
There are a few places with only NDB/DBE let downs. They are the least expensive let down aids available to an airport authority. Such airports are unlikely to ever be able to afford a localiser or have a VOR positioned on thier field.
I hear you say what about GPS approaches?
GPS approaches suffer from a significant limitation. They require an approved panel mount unit. Now we all know most people will "supplement" such an approach with a GPS (hand held or otherwise). However, strictly if the ADF is removed from the aircraft then these approaches will become illegal for most GA unless they invest in an approved panel mount unit.
The use of hand held GPS units for en route or approaches in not likely to be approved any time soon!