I disagree on the first point. Don't we learn more about technology in general the longer we wait? The price/performance of technology goes down while we gain

I disagree on the first point. Don't we learn more about technology in general the longer we wait? The price/performance of technology goes down while we gain more technical options, and we learn more about the trip. There may be other reasons that it's an issue (orbit locations?) above and beyond the valid one that you listed - these grand projects exist at the whim of the president's successor.