I don't know how serious this topic is, and I know I don't post or visit here much, but there are a few of points of consideration.
The first is the fact that Vince set up his Iron Tower Studio forum. I think that quite a few of the more serious posters that were still around now have two places to go and see, so you'll likely get fewer of the "good" posters spending their time here since their energies are split. And since ITSF are more strongly moderated, there probably won't be as many people
Second is the fact that quite a few people like Section8, Vault Dweller, Naked Ninja, etc. started working on their own games; isn't it likely that these people, who probably would have been making the majority of the good posts, now don't have the time any more, or even as much time? Also, given that there are a lot of lulzers, even if they (or someone else) do make a post, it's likely going to just be ruined, or turn into another piracy/decline of the codex/multiheaded dicks thread.
The third point I'd like to mention was something I've noticed recently is, to be honest, stupid threads outside of General Discussion. I don't mind a lul or two, but it seems like General Discussion is the new Retardo Land, and places like Feedback seem to becoming the new General Discussion. I do see how they are classified as such, but they then appear on the front page. This was particularly noticeable after the GD threads were removed from the front page. It almost seems as though people are trying to see how many retarded threads can appear on the front page.
The fourth is the tl;dr factor. I've got lots of weird ideas for computer games that come to me in dreams. Occasionally, I'd like to write up some stuff to see what other people think. I can't work on them at the moment, since I've already got two games in development at the moment, and I have very little spare time as it is. I'd like to write a long post. But why bother? Hardly anyone spends the time to read long posts, and I guess I'm fortunate in that I usually have to save posts to my computer so that I can read them later given the small amount of time I have access to the Internet in a day, so that I can. But even so, why bother when the chances are high that about 12-15 people maximum will respond, and if it's more it's probably down to someone posting something stupid?
I used to enjoy coming here, even if it was for lulzy things like demotivational posters or rat diplomacy - particularly when it's computer game-based or RPG-based. I'm not against lulz. I just think things have tipped too far towards that now. It's a bit disappointing, but I'm not too fussed. It's probably more disappointing for people who have been here longer or who come more often, and I don't really have much spare time anyway.