It's true that there is a rural/urban breakover point; I'd contend that is at far greater densities than most people think, especially if we made use of the entire spectrum rather than the drips and drabs meted out so far by the FCC. The portion of the population getting shafted right now, all the "rural" (and most suburban, and urban in Texas-style "sprawling" cities) folks, is definitely a majority. "Laws of physics" arguments aren't convincing at this point, since engineers have had their hands tied by FCC regs. Let a big market for this type of radio tech exist for a decade, and then we'll see what can be done.
You can't use the entire spectrum without addressing the sunk costs problem. All the existing users of the spectrum would have to throw out their equipment and replace it with spread spectrum equipment. Nobody wants to do that, especially when the benefit of them doing it goes primarily to third parties. You want to talk about phasing it out in favor of spread spectrum, fine, but that's going to take years or decades. What do we do in the meantime?
The next piece of trouble is, if you really want high power unlicensed spectrum, what do you do about contention? What happens when scientists start setting up transmitters to continuously send 50Tbps of scientific data from remote monitoring stations to the regional university's data center? Or people set up a distributed mesh network of Tor nodes? Or someone decides to operate a wireless "cable TV" franchise and starts transmitting 50,000 streams of 4K HD?
Don't get me wrong, I think you have the right idea -- spread spectrum is the way to go for wireless and there is room for a lot of innovation there if the FCC would get out of the way. Especially in the way of short and medium range mesh networks. It just isn't a replacement for fiber to the premises.
