"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).
The Biden administration is making a fool of itself in yet another way. Europe uses these same C-band frequencies and U.S. planes have no problem landing there. To think that we can't land a plane in the U.S. unless the telecoms give the FAA a few billion dollars is absolutely ridiculous. This was studied years ago, a solution was found years ago, and now they think it is a problem? Get real. Let's Go Brandon, turn on the C-band 5G towers.
I thought the same thing, but the data shows that the unvaccinated are the only group to have a higher proportion of tests than positivity, so even when the unvaccinated get tested, they are less likely to have Covid.