The greatest limitation on advancement and exploration of space is man. We had a fast-moving space program, only to have it dismantled by greedy people demanding we stop spending money on space exploration and start giving it to ourselves (as in the “war on poverty” where poverty won).
As long as our civilization regressive to an inward vision, we will not even get back to a glorified school bus in orbit (space shuttle).
If we want to advance, if we want to explore space, it requires recapturing a lost set of core values we had as Americans conquering those first waddling, infant steps into space and the moon. The core values of a centuries-old American culture, where rugged individualism and self-reliance were far more common, and focused on the common good.
Our Orwellian “progressive” European-oriented culture and it’s multiculturalism are a wasteland for innovation and advancement beyond our little solar system.
Indeed, we are the greatest obstacle to overcome.