This book seems insufferable, at least based on the review. Half of the review is trying to poke holes in why people won't live on mars and the other half is about how people trying to pursue goals such as this are self-serving and corrupt. I'm sure a market exists for this kind of book, but to me it's just exhausting. What's the harm in trying to go to mars if it results in decreasing the cost of space flight by 99%…
Maybe I misunderstand your comment as if we've run out of ambitious things besides those that border on science fiction. In that case, I think the market is those of us who think there are more tangible ambitious things right in front of our faces. And in front of those with the resources to make a difference ie, fighting starvation, authoritarianism, inequality, disease, genocide. Are these too boring?
Going to Mars and living forever are primarily technical problems.
Starvation, authoritarianism, inequality, and genocide are primarily political problems.
The resources and skills used to solved the former set aren't broadly applicable to the latter set, though it is easy to find examples of people who are good at solving one of these sets of problems who assume that they'll be good at solving the other set as well.