There are and have been lots of people doing great work without generating large investment returns, because they aren't doing the kind of work that generates large investment returns at all.
(If you're looking for greatness on their scale, then of course the number will be "not that large" because work that great is very rare. But there are plenty of artists and scientists and whatnot achieving lesser levels of greatness and most of them are not getting large investment returns.)
Bach, Mozart, Beethoven. Newton, Gauss, Euler. Dante, Shakespeare, Goethe. Faraday, Darwin, Einstein.
(If you're looking for greatness on their scale, then of course the number will be "not that large" because work that great is very rare. But there are plenty of artists and scientists and whatnot achieving lesser levels of greatness and most of them are not getting large investment returns.)