I don’t want to call the ISS a waste of money, but our part of it could have been used to establish a permanent location on the moon. We could have possibly have harnessed the hydrogen 3 that is just laying on the surface to spring board us to Mars.
I do not have enough practical knowledge about Hydrogen 3 to have a helpful opinion.
As to man in space - for the next 100 years - I see no possible profit generating activities except Space Tourism and Space Thrill Rides.
Where can we go, besides our Moon and Mars?
Venus - deadly heat, deadly atmosphere, and deadly atmospheric pressure.
Jupiter moons - bathed by deadly concentrated solar radiation in Jupiter's huge magnetosphere, as well as by several deadly radiation belts.
If we had committed all of our ISS funds to the robotic exploration of our own Solar System, I think we would have learned essential facts about human survival in space, other essential facts about planetary mineral wealth, and essential knowledge about space robotics.