What about having a group of people of different "ages, interest levels, and experience levels" makes in-depth discussion impossible?? I would think such an environment would foster discussion, since everyone will come in with different questions, concerns, and perspectives.
Besides, where can you find a community where everyone's the same...?
Ahh... how do I get into this without sounding really arrogant.
I have a lot of trouble finding art books that are useful to me.
When I first started drawing, there were tons of books on how to use simple shapes to make faces, how perspective works, and basic art composition. Now those books don't tend to contain anything new. More advanced books get very "here's the perfect oil painting technique for rough sees using a palette knife", so if I'm working on something new in art, I often search for months to find one with the information I need.
Diverse experiences are good. Diverse skills levels... are best for people who are just starting out. We have plenty of 101 technical threads. "how do I write good dialogue" or "help me with grammar". It's not that I claim to be perfect at these, but I've been around the block enough that I don't tend to see anything new. I can only really give advice and encouragement.
The more specific and complex the issue, the more likely it will be
A) Totally irrelevant to most people here and clog up the forums
B) People will lack the background to answer and either not answer, or give information that ranges from useless to incorrect
So if I want to say 'hey, does the pacing in chapter three feel okay', forums can be very helpful, but if I want to say "I need advice for making this character's highly specific verbal choices not control their characterization" I don't tend to find forums very helpful, at least not ones that aren't geared to narrative theory nerds. Even if there is one or two people who have really amazing insight, a thread is not an easy place for a long, dense conversation. It feels like walking into a local family game night and demanding people teach you the finer points of Shogi. Is there a chance some Shogi nerds are there? Probably. But are you going to mostly annoy a lot of people and get a few people reading you the wikipedia page on Shogi? Probably. I'd rather find a Shogi club and go there.
The discussions you wish people were having are happening, just not at a level that interests you. Which is why discussions where a beginner and a master can both have valid input, like genre and morality, get far more interaction. And if you want threads that aren't just the basics, a general forum isn't the place to look.