If a high-speed rail line would run long distances in the middle of nowhere, that's usually a sign that you should not build the line in the first place. There are rarely enough end-to-end passengers on any line to justify the investment.

The Central Valley is sparsely populated at the moment, but it doesn't have to remain so. Expanding the cities there by 5 or 10 million people might actually make the high-speed rail project sensible.