The easiest way to find out why people no longer post is to ask them. I'm an administrator on a mountain biking website, and have the facility to 'e-mail all members'. Why not do this asking why they don't post anymore or as much. Admittedly you may only get a small percentage that reply, but at least it should give you a starting point on why the post count is not as high as you'd like.
It would be helpful too if people would explain their statements. If someone thinks the site is 'elitist', then what gives that impression ? This is not meant as a criticism of anyone's post, just may help the site break down the 'barriers' that people think exist.
I don't see the forum being 'elitist' myself, except where people try and post threads on topics other than pre 67 cars, then they are 'put in their place'.
As I said earlier, it's a target audience out there for stock pre 67 cars, just look at the membership of the Historic Club, not as high as other clubs because the target audience is lower. Why not advertise this site more at shows such as Stanford Hall and Lavenham ?
I for one would like to see more traffic on this site, but don't want to compromise the quality of the topics to get that traffic.
A day may come when the courage of men fails, when we forsake our friends and break all bonds of fellowship, but it is not this day.