There's no suggestion that Euler is anything but an individual example however it is explicitly stated that number of works was a measure of productivity not quality.

If you want to split the difference on the age of mathenaticians I happened by chance to be in Adelaide in 1985 when this was snapped: https://en.wikipedia.org/wiki/Terence_Tao#/media/File:Paul_E...

Not all Groupies die young, https://mathematical-research-institute.sydney.edu.au/news/p... is still grinding along having created and steadily expanded on a system from 1980 through to today that is still actively used to beat quantum cryptographic cipher candidates.