Wireless coverage above >30 MHz or so (too high to propagate by ionospheric reflection) depends on line of sight to operate. The cell network works because people invest a lot of money to provide electrical power to very high points above the surrounding terrain.

The only places that community meshes (wireless meshes without $$$) can work are mountains with cities below them or mega-cities where residents have access to the roof tops of their buildings.

There is no amount of power, no special modulation, nothing, that can punch through a slight hill or a valley. Your antennas have to be above the surrounding terrain to get a high data rate mesh to work. And for most places that means spending money to get access to rooftops or towers. Everyone just adding their node in their house, car, or as a phone is not going to do it.

tldr; the only thing that matters is height above terrain and that costs lots of money.