At the moment.

Laws of physics tend to change infrequently. Sharing spectrum means low speed for all.

I'm not suggesting that, but that economics changes things much more rapidly, c.f. 5G, which may roll out multi-gigabit speeds to consumers far before landline.

And how you will provide multi gigabit speeds to a 100 people in close proximity simultaneously? There is the question of throughput of the whole network.

So beams must be directional, to avoid sharing of spectrum with all, but only with some.

A fiber of glass is the ultimate directional antenna.

The problem is that broadcasts are exactly that: broadcasting. They transmit in all directions. While you have bandwidth constraints in wires, they're all localised to the wire. Even parabolic dishes (which make getting a signal a huge PITA) still aren't as localised as cables. Wired connections get a bad rap, but they're actually a much more preferable (and scalable) medium for transmission than radio waves.

Not to mention that "bidirectional beams" is another way of saying "noise".

why can't TCP/BATMAN be defined as "decent internet access"?