Quality means many things... When it comes to the experience of the people using the site, performance - how long it takes the requested page to display - is critical; the vast majority of Stack Overflow's page requests are someone requesting a page that they urgently need to read.

That doesn't preclude other aspects of quality of course. But it does influence how they're approached. A heavily abstracted system that hurts performance is unacceptable, but there are other ways to achieve the same ends.

You might find this article interesting... http://samsaffron.com/archive/2011/03/30/How+I+learned+to+st...