This caveat destroys the rest of your points, as logical as they may seem.
Remember the original argument was "I think public transit will continue to dominate in parts of the world where it currently dominates" I'm taking that and strengthening it to a significant expansion of transit, but obviously not everywhere can do transit.
If the lanes on the road can fill up, you have enough traffic to sustain some busses.
In emptier areas that's a pretty different discussion, but importantly you still wouldn't need to design around cars. Slap in a very basic road and it'll handle all the cars fine.
No one was suggesting that.
> I can carry many items in its trunk, making it worthwhile to make multiple stops on my journey. Public transit is not meeting my use-cases.
Well the guy I was talking to was only worried about one or few trips per month, and we only need most people to use transit for the scenario to work.
Ergo, it's no surprise that people want to use them as often as possible. They want to recoup value from those fixed costs. It's simple economics.
> in the context of waymo there's no effect of "I'm already paying a ton of money to own and insure a car, I might as well use it every trip"
If you do that once a week, then you can use transit the other 90% of the time. If people use transit 90% of the time, then we can build smaller roads and de-prioritize cars. That's the argument here, that transit can dominate in co-existence with self-driving cars, not that we'd need to get rid of cars. And especially in the context of waymo there's no effect of "I'm already paying a ton of money to own and insure a car, I might as well use it every trip".
(And again, this is in moderately dense areas where transit works and you actually care about how many cars are on the road to begin with. And it doesn't have to be 90% in particular.)