Is there a difference between YA and general fiction beyond marketing? If you think it might be more profitable and/or enjoyable for you, I say go for it. I'm not sure what's going on in the world of publishing, but I and quite a few of my friends turn to the YA shelves when looking for really good new fiction these days. I'd rather read Neil Gaiman, John Green or Garth Nyx than James Patterson.

Thinking back to my YA years, I was reading Frank Herbert, Isaac Asimov, Arther C. Clarke, J.R.R. Tolkien, ..., etc. As were most of my friends. Yes, there's a lot of rubbish on YA shelves, but that seems prevalent everywhere. Just because it's marketed to a younger crowd, it doesn't have to be dumbed down. I often find it's quite the opposite. I think you're right about the younger crowd having a larger percentage of "open readers".