Colonizing is Mars unrealistic. Mars is too hostile for our type of life. Maybe machines can "live" there. Developing the science and technology to make Mars even slightly more viable is going to take a long time and we're going to need a healthy Earth while we work on the solutions anyway. So why not make sure we have a healthy Earth in the first place? We can keep an eye on Mars as a stretch goal but it's always going to be pretty far down the priority list. I know that's not the romantic view.
No mention in TFA of O'Neil cylinders or other near-earth space settlements. To me, these options must be mentioned in the same breath as "Not Mars", because we do need to escape the cradle.
