In your scheme we would have a few individuals visit another world. How do the other 99.99999% of us have the experience? It is vicariously through their experience. I would rather have virtual technologies developed that would allow the common person to closely experience the other world through interfaces than read about some individual landing on another world 1 time a decade for the cost of a 100's of billions. The only advantage of having humans on another world in a flag and footsteps mode is to say we did it (ala the moon). I would much rather have sustainable steady reasonable exploration that continues to maximize science return for cost, and provides all of us with richer virtual experiences.

Manned exploration will come. I have no doubt of it. We will build vast structures around our sun utilizing materials of asteroids and moons with automated robotic systems, and populate those structures. Rather than a dark ages you seem worried about, I see a blossoming of humans and multiplication of our individuals so vast that it staggers. We will be trillions eventually rather than billions. We will have access to the vast resources of space and ala star trek, humans will be able to quit worrying about basic needs, concentrate on acquisition of knowledge and advancing the human condition. We just will have to agree to disagree on the path to take to get there.