> If we continued on the trajectory we were on in the 60s we'd likely already have human outposts, if not civilizations, on the Moon, Mars, and perhaps even some of the outer planets' moons.

I was amazed when I started looking at old maps of North America and realized how short a time it was between Columbus stumbling across the West Indies and a wave of explorers/exploiters mapping out the western hemisphere.

(Obviously it's a vastly different situation than we face in space, and based on what we're learning about biology in space we might well have abandoned any such outposts by now, but your lament is well-taken.)