That doesn't have to stop us from much more practical and realistic striving though.
We have an entire universe in mini right here around us in the form of our own solar system, filled with so many resources that we probably couldn't over-consume them in millennia, and possible extra-planetary homes for billions of us using technologies that are just this side of realistic.
We're still talking about at least decades of fantastically costly investment, but at least it would begin as investment for a shining future within a human lifetime.
Colonizing the solar system doesn't sound as impressive on text as stories of strange and wonderful alien landscapes in distant star systems, but I don't think anyone being able to gaze with their own eyes from the peaks of Verona Rupes 90 years from now would care.