If we insisted bicycles only be allowed on dedicated bicycle tracks, there would be no track because there would be no bicycles (because there was no track!)

As a bicyclist, I would love to have a dedicated network of bicycle track all over town. But it doesn't exist, yet.

Also, this is way fuzzier than you present. There's little conflict between cars and bikes on lightly traveled, spacious suburban streets or sleepy neighborhood county roads. Even on collectors & minor arterials, on an e-bike I travel about the same speed as a slow car.

Speed delta is not an incorrect observation, but varies in significance. In terms of priorities, highways are certainly top candidates for the first dedicated bike tracks.