It's many factors. However, the inability to create new cities and infrastructure can be overcome with will.

Now, whether we need new cities is a separate question.

In Canada where taxation and housing is expensive, the complaint has been that fertile landed is being used for urban sprawl.

One potential solution, that's rarely discussed, is to build cities in the North adjacent to large bodies of water. With access to shipping routes, lower taxation and superior infrastructure to make up for the adverse affects of weather.

You may argue the economic incentives and capital aren't there. I'd argue there's a massive misallocation of capital and the economy is fundamentally broken, but that'd be a lengthy discussion.