Doug Messier has a critique, with which I largely agree. He does seem to be laser focused on solving the transportation problem (which was the first one he encountered when he tried to implement his initial Mars plans). I emailed him years ago about the fact that we have no idea whether or not we can conceive/gestate in 0.4g. His response was basically, “that’s not my problem right now.”
But this blinkered mindset may not ultimately serve him well in terms of his long-term goal. It would be tragic for him if he solved the transportation problem, but not the biological one, and his dreams of Mars colonies ended up being still born, despite the cost reduction of transportation there.