Exactly, Udacity is essentially a more interactive version of w3schools and other tutorial websites. With a more expansive collection of areas of study.
The problem stems from this statement, the crux of this post: "Is Sebastian Thrun's Udacity the future of higher education?"
That's where the negativity comes in. As you said, Udacity won't make you a world class computer scientists, but that's what universities like Stanford, MIT, UW, Michigan, Caltech, CMU and other top CS schools are /supposed/ to do.
If you want to learn what AI is generally about, Udacity can help. But if you want to build a career out it, and become and actual expert, these sites fall flat on their faces. By embracing Udacity and Coursera as tools of higher education, Stanford and universities that follow suit are damaging the quality of the education they provide.