Taxis (and Uber etc) also take up space on the road when they only have their driver and no fare paying passenger on board, so I don't see that a Waymo is any worse than that.

Both human-driven and robo-driven taxis are financially incentivised to spend as much time as possible carrying fare paying passengers and as little as possible driving empty to pick someone up.

Anyway, I agree that walking, cycling, and public transit, are all IMHO preferable to any form of taxi.