> Are Ivy League colleges famously demanding?
Yes, absolutely. They demand a lot of hard work, much more than your typical public university. As you go through life however, you start to realize that accomplishment comes from working hard on the right things - a subtle but important distinction from plain old hard work.
Imagine that you are running and come to a wall. You are big, strong, and have lots of resources at your disposal. You almost certainly can bust through the wall and keep going. Do you do it? Or do you check to see if there is an unlocked door around the corner? The reward for you is exactly the same (a grade of A in the class; a promotion at work) and you aren't the person that has to clean up the mess you leave behind. What do you do?
The Ivy League schools have plenty of people that would choose one option and plenty that would choose the other. The other schools don't have very many people for which busting through the wall is even an option, which is definitely not the same thing as "working harder"