I want to use my phone as a GPS, but I don't want to turn on high accuracy to assist Google's wardriving. What am I to do? I like using my phone as a GPS.  It has all the sensors and storage and everything.  Even if I can't find a good app yet.

However (since I am concerned about leaking private data, I have turned the location setting to device only, which means it only uses the GPS radio), Waze constantly nags about turning on "high accuracy" location; meaning it wants to scan wi-fi, bluetooth, and everything else.  Which means that the OS will be shipping that info to Google/Alphabet HQ.

How can I use my phone as a GPS without assisting Google's wardriving efforts?  GPS by itself is highly accurate, or at least it was until Google decided to harvest wi-fi locations via a distributed Android network.  Or am I misremembering something?

Are these nags just part of apps, or is there something I can do to mitigate incessent nagging?
You can use the "Device only" location mode, found under Settings->Location->Mode. The key performance impact of this setting is in the time to first location fix. It can take minutes to find your location initially, but later updates will be quick.

I am not sure whether you also need to disable use of WiFi and Bluetooth for scanning purposes, but if you are concerned about privacy I would disable these:
Settings->Location->Scanning