Well, the forum may look dead to most people, but that is simply because it's been very active, with more than 10,000 members, for a long time, since 2004.
That was when the series was showing for the first time of course, it was very popular, so there was a lot of buzz about new episodes, cast member gossip and such. It's bound to become a lot less active after a while, after nearly 30,000 posts about loads of subjects and more than 10,000 Gallery images, so it's more like, been there, seen that. You can also tell from the number of recently released DVDs sold from the UK. Season 1 has only sold a few thousand copies so far, and the following seasons (for the first time ever on DVD!) even less, so while that number says nothing about downloads and streaming, it's still indicative of waning interest.
That's why we also hardly care about spoilers, because the series ended in 2006, there have been and are lots of ways to watch it, although we can only be grateful that MITM still appears somewhere in reruns.
I'm glad you get a lot of messages from fans. I hope your fansite will be doing well.
Rich