That sort of long run probably has even longer timelines than 75 years, and that's an argument which carries almost zero weight to an investor (particularly relative to the one SpaceX is actually making which is using their launch monopoly to make massive profits meeting 2020s inference compute demand) because by the time it happens, assuming it does, the space market is unrecognisable and they've missed a whole bunch of other hype cycles. The bull case for SpaceX depends a lot on what they deliver by the mid-late 2030s being more than expected rather than less and essentially not at all on the constraints and challenges of next century.

[1]I also hear this thesis every week from my own CTO, but much as some VCs like the passion it's not why people fund us...