In maths though there was some fluctuation. Mathematics in Roman times saw a decline, and in medieval times a complete breakdown (at least in Europe). If we take Euclid to be the bar for a first-rate mathematician, then there were none in medieval times, but later there appeared Gauss, Newton, Leibniz, Euler, Galois etc. I’m also not sure if today anyone clears the bar for Hilbert-level genius. So I don’t think the bar for “top 10 today” keeps going up. From time to time it goes down.