People definitely still buy cardbacks, in fact depending on condition some cardbacks go for more than loose figures!! If no one on JD is interested, I am sure you can find hits on the various Facebook groups dedicated to vintage.
AFA is still around, don’t know what is up with their website, but despite competition from CAS and UKG they are still in business. I personally am not a fan of grading loose figures, they lose their charm being encased in acrylic in my opinion. But if you think you can get a high grade, then there is that premium you obtain for resale value.