Computer science is an extremely young field. The parts of the field that number theorists could dabble in quickly got fleshed out and got hard as they could apply the millennia of accumulated number theorist knowledge, the parts more related to how to work with computers (such as algorithms or program structure) is still young today.
Edit: Note that the frontier of the field will always be extremely hard no matter what time you live in. The reason is that things will be poorly understood and written, there will be no good textbooks or explanations, you have to trudge through all that often without anyone to help you understand things or correct you. It took centuries for calculus to become as easy as it is today.
Edit: Note that the frontier of the field will always be extremely hard no matter what time you live in. The reason is that things will be poorly understood and written, there will be no good textbooks or explanations, you have to trudge through all that often without anyone to help you understand things or correct you. It took centuries for calculus to become as easy as it is today.