Just look at the Top Posters(All Time) on the side of the page. At least 4 of those haven't been here in two years. I know at least one has passed on but many of the old voices have moved on.
As far what might keep people interested is if there were many great mysteries left. But for the most part, they have been solved or have proved unsolvable. That is the great benefit of this site, much of the documentation on those mysteries can be found here(bird glass, etc.).
And yes, I do think Facebook groups has diluted the pool of visitors. Some of that may also be affected by many of those remaining tend to be purists. The traffic I see in most of those groups are mainly those with what I would call Camaro clones, restomods, Pro-Street cars, etc.
As for me, I'm not sure there is much more I can do. I have my coupe and convertible projects done. What would interest me at this point is a true Ram Air II or similar car. A GTO Ram Air II Auto car just got bought last week(yes I hadn't pulled the trigger after several months of staring at it), that was likely the last car pre-smog era car I would have considered. Perhaps if I were to come across a Ram Air IV GTO Judge or a Lucerne Blue '70 T/A or a... But price tags on those cars remain high with uncertain payouts and with 4 cars already and no space, something needs to get sold. But all those things are personal problems.
To get back on point, yes, the times they are a'changin'...
1968 400 Coupe, verdoro green, black vinyl top 1968 400 Convertible, verdoro green, black top 1971 Trans Am, cameo white, auto 1970 Buick Skylark Custom Convertible 350-4(driver)