Most investments are probably pretty replaceable though.
By this, do you just mean that the selection of one investment over another usually doesn’t matter? Or are you saying overall investment is replaceable in some way, i.e. my increased investment can lead to someone else investing less?
As part of the pros/cons between “give now” and “invest now, give later”, has there been any investigation into how much good is accomplished by investing itself? It seems like that is a (small) part of economic growth and innovation, so I’m curious if there’s much reason to think that has a big enough impact to include in the invest-then-give decision.