Sure, filtering out undesirables helps a bit, but you're never going to be able to filter out all of them unless you go private and have strict vetting, which clashes with the whole anonymous aspect.

Instead of complaining about the cultural and generational shift of the web, create something new and hopefully influence future shifts in a more positive direction. Everything declines, you can either succumb to it, maintain it or move on and create something new. Such is life.