Most gun clubs are forcing the membership to be members of the NRA because the NRA gives them a break on the insurance if all gun club members are a member of the NRA.
I suppose it's more a question of economics; is it cheaper to have the insurance and have a percentage of the membership not in the NRA? Or is it cheaper to have the insurance, pay the full price, and not be members of the NRA?
The position of the NRA on various issues in various areas is a different thread altogether.
The Wildlife Management Areas are few areas that don't require NRA membership, but do require hunting licenses for some reason or another.
There is Swan Creek, Skyline, and so on.