"5G requires cell towers on every city block" is only true for the millimeter-wave band frequencies. The frequencies that the FAA is arguing against is the about-to-be-released C-Band frequencies which penetrate much better and doesn't need many more towers than existing 4G services.
Your points on Li-Fi are good arguments against millimeter-wave band frequencies, but to be honest, that isn't the future of 5G (likely limited to stadiums and very busy city streets).
"5G requires cell towers on every city block" is only true for the millimeter-wave band frequencies. The frequencies that the FAA is arguing against is the about-to-be-released C-Band frequencies which penetrate much better and doesn't need many more towers than existing 4G services.
Your points on Li-Fi are good arguments against millimeter-wave band frequencies, but to be honest, that isn't the future of 5G (likely limited to stadiums and very busy city streets).