Over 14000 members but only 22 left with more than 400 posts.
You should if you look at how little good content is added each week.
Honestly, it doesn't matter if six people make up more than 1/5 of those 50k comments. It's a fact that most members of any community tend to be lurkers; then you have those who are active for a while and lose interest, or those who sign up, never comment and then disappear. Sustained activity - even just among a few members - can actually go a long way in encouraging participation by others.
Besides, I have yet to come across a single forum where half or even 1/10 of the content is what you would consider of quality, which is something that is extremely subjective in itself. Why hold this particular forum to such unreasonably high standards? You don't need to have good content to have a good forum.
EDIT: Before I forget: congrats on the milestone (both post count and upcoming anniversary)!