Yes, but it's very different to say "you should hedge against the case where you get a medical disability and the Singularity doesn't happen" and "you should do what would have put you in the best position today."

Of course. The future will be different from the present. Strategies that work today may not be viable tomorrow (just look at CD rates from the early 80s and contrast with today). However, if you assign a reasonable probability to the United States maintaining political and economic stability, and for money still being important, then some level of saving for the future seems to be a safe bet.

It is not enough for me that I won't be taxed on the money after 2048 once I start to draw it down; the cost in flexibility from not being able to invest it in a Bitcoin-like opportunity is really high.

It depends on the person. If you're the sort to be active with your money and seize opportunities, that's one thing. If you're the sort to spend money on frivolities, then tossing a certain portion into a retirement fund isn't a bad idea.