Dying off? You do realize that comics are still being printed and that many of these modern issues are selling for four figures. Instagram is filled with 20-something collectors who can't get enough of comics from all ages. And the movies and TV (Disney Channel - WandaVision, etc) are being fueled by comics. Trust me, comic collecting has exploded in popularity and the prices being paid for graded comics reflect the current state of the hobby.
These comments prompted me to look up some comics on ebay, and I see that even my Star Trek Gold Key/Whitman comics are back in demand. Those ran from 1967 into the late 70's. For a while, when I was trying to sell them off there was little interest, so I gave up. I hope shows come back soon, maybe I can sell the 1-61 run to a dealer.
Unfortunately, I don't think I have any DC books from that far back. Probably some Batman books back to 1984, and a long run starting around #400. There are at least 4 boxes of comics here; I never really gave any thought to grading them, and I think it would be more work and expense than I would want to commit to. Aside from the grading fees, I imagine the shipping adds up quickly! Those full long boxes are now too heavy for me to pick up
Thinking on it further, it might be worth grading the first 10 or so Star Treks, with the color photo covers. As I recall, they are in pretty nice shape.