Any community will only be as good as the people in it. Yahoo answers was a ridiculous troll-ridden stupid fest. Quora came along, and for a while, it was good. Now it has reached Yahoo answers level of stupidity.
If people make shitty content, and the majority of the community consumes and likes it, then the problem is a tough one to solve. If you wanted an elite group of high quality content, you used to have academia, but even that is going through ridiculous issues because nobody reads and nobody cares.