OP here - thanks for all the thoughtful responses!
We have talked to realtors a couple of times through these many years. No realtor wants to touch it, for the many reasons highlighted in this thread, plus the local realtors know it won't sell.
This thread inspired me to look deeper into the online presence of this county. It was not easy for me to find (so I missed it on the first pass - operator error, I'm sure...), but I did find a GIS with property records with enough detail to find adjacent property owner's names and addresses. I may pursue that angle. I also discovered that the lot is nominally 0.5 acre, so bigger than I remembered. There was a road cut in in the 70s and you can still see the vague outline on the satellite image. I don't think the lot is landlocked but I don't know who "owns" the road, but it is not county maintained.
I followed the link above (buys unwanted property) and submitted a request for my all-cash, quick-closing offer. We will see what comes back. I expect to be ghosted, but if it is anything above nothing, we will likely take it.
DW is campaigning for us to take it (my sisters would gladly deed it to us) to ensure it never gets developed. The taxes have gone from about $12/year to $24/year since about 2000. That feels like it may be a noble use of the asset that matches our values. OTOH, I don't see the adjacent area getting developed in our lifetimes, so I am not sure we are really preventing anything. It is not a place we would ever go and "hang out" - 3+ hours from home, steep hike up to an overgrown side hill lot. We live in 12 acres of gently sloping mixed hardwoods already.
Thanks once again to all that responded. The responses we helpful and actionable. This is an example of why this is such a great forum!