On the other hand, most modern mathematicians know stuff that would blow Whittaker and Watson's socks off. Much mathematics is obsoleted. For example, there w

On the other hand, most modern mathematicians know stuff that would blow Whittaker and Watson's socks off. Much mathematics is obsoleted. For example, there was a lot of incredibly difficult mathematics for finding areas under curves, which was all completely obsoleted with the discovery of the fundamental theorem of calculus. Nothing of value was lost. Individual pieces of mathematics come and go from general awareness, but the overall trend is definitely one of increasing, not decreasing, understanding.