One of the strongest arguments for heavy foreign aid and development in my opinion is the squandered human potential. The man or woman who could be the next Einstein may well be tending a cassava field right now. That's our loss as well as theirs.
Was there an assertion that there isn't a return on investment? Asserting that the inevitable outcome of rampant income redistribution is systemic collapse is compatible with "investment in personnel has returns"
Forcing the most productive workers to subsidize the consumption of unprofitable workers always leads to failure. "How am I to eat when I only grow 10kg of wheat a year but need to eat 11kg? We should use the state's violence to take 1kg from the farmer who grows 20kg and eats 12kg, Now I can grow 13kg of wheat for every 12kg I eat! A net gain in production!"
It's a misallocation of capital, simultaneously (the apparent) investing in the more profitable producer would have been better and (the non apparent) that deluding the worker into believing farming 13kg of wheat for every 12kg increases the price of the input goods and input labor for other industries.
Marxist Communism's argument is essentially: "While capitalism's losses are privatized, the fact that the profits are also privatized causes everyone to suffer. Instead of allow bricolage economics, the state's central planners will be to sole source of investment and sole consumer. Profits will be nationalized but losses will also be nationalized."
Having that state be the sole investor in an economic -- a monopoly on entrepreneurship -- dooms it to failure. It does not mean "investments [even centrally planned ones] don't returns"
Probably not. Einstein was not a solitary genius. He lived in a culture and society that placed high value on learning and especially math.
He was also in communication with some very gifted people such as Emmy Noether who actually discovered the mathematical foundation for much of his work.
Srinivasan Ramanujan on the other hand is a much better example of finding someone who had super human abilities in an unexpected place.
Thus the aid, to attempt to create that society.