I'm as wildly supportive of space exploration and colonization as anyone, but it's quite true that both economics and logistics argue against offworld human activities as a solution for any of Earth's major problems. Beamed power from extremely large solar power satellites is one possible exception; building these would almost certainly require a human-supported infrastructure for lunar or asteroid mining and orbital construction.
As someone rather depressingly pointed out, until we're building cities in Antarctica, cities on the Moon or Mars will not make economic sense. Antarctica is orders of magnitude easier to reach and to live in.
So, if we end up with significant offworld colonies in the foreseeable future, it will be for reasons which are not purely economic. Many have speculated on what might provide the motivation to make this happen. So far, nothing in the real world has come close to providing such motivation.