Yes, no one is a renaissance person any more. But I don't think that there were as many renaissance people in the past as we think. Admittedly I don't have much evidence for this. In the case of maths, I think our idea that many more mathematicians used to be polymaths in the past is slightly skewed dues to the fact that until about 2 centuries ago, 'mathematician' and 'physicist' were not distinct categories. We think of Gauss and Euler as polymaths, but Euler was by all accounts a terrible philosopher.

EDIT: I just remembered that Gauss was an extremely competent philologist, so maybe the above is no longer valid.