I don't really want to discourage anyone from posting in Progressing Games by imposing too-high standards. That's the place where anyone can set a project started. Consequently it'll be full of non-starters, but at least it provides some small opportunity for at least one of them to develop.
The Showcase, on the other hand, is for the games which are actually properly being made (that's why it's a separate section). There are significant (subjective) restrictions on which threads belong in there, and it's basically up to me to decide. People need to ask me to look over their threads if they want it moved into the Showcase (I won't spontaneously do it myself), and that hasn't happened in months. I've not looked at the threads already in there, though, but if you have a list of threads which you think don't belong in there, you can PM me with it and I'll look at them.
Frankly, when I was a member, I never looked in those sections. I was just here to improve Essentials. I don't know what the quality of games used to be and what it is now. Certainly the Showcase should be full of good games (or at least promising games; I'm not sure about making it a playable demo/completed-only zone), but the main problem really is that people simply aren't finishing their games, primarily because they want them to be too epic. The way people think about their games is entirely too limited, and that's one of the things I want to address. It'll be a slow process, though.