Simple things on the outside often are quite complex inside, and opposite is also true. For example CodeIgniter is much more simple than Yii, buy it is more diffecult to use, for example it is not IDE friendly.
I disagree that simplicity is the main virtue, I think you mix simplicity and well build. Well thought out things usually works as simple possible because complexity adds upp very quickly, and not optimal solutions just would collapse under its weight.
Everything should be made as simple as possible, but no simpler
Original: It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience. Albert Einstein