I originally joined during the '05-'06 season. Even then people were saying the site used to be more active, and it seemed true based on reading old regional threads. It's tough to get solid numbers because the site has been through multiple owners and multiple software systems, but I think 2 graphs are illustrative.
First, registrations, which peaked in 2007. I'm not sure what that bump in 2015 is, but safe to say that it's an anomaly.
Second is posts. All of the posts prior to mid-2004 were purged at some point, so that data is unavailable. From then, posting peaked in spring 2009 and trended downwards from there. That dip at the end of 2010 was when the site was hacked and the database crashed. After that, I took over.
I will certainly shoulder a good amount of blame because of my neglect. There are a lot of things that I could have done that would have helped sustain the site. I think there are also other factors involved. When I first joined, the site had a reputation as a sort of troll haven. A lot of posts were irrelevant and, dare I say, vacuous. While I enjoyed a lot of that, I think that rep kept a lot of people away. This also coincides with a general expansion of online communities like Facebook and Reddit. It is a trend across almost all web forums that activity has been decreasing since then.
I am a little confused about some of the posts about buying the site. I have only ever received 2 inquiries. I will entertain offers, shoot an email to david@ this domain.