That's why you have to build and live more densely. The US absolutely refuses to do that, outside of Manhattan and a few select other places. It won't be a place where local trains make any economic sense until this changes.
However, for your "door to door" point, that's not desirable anyway. Even here in Tokyo, you have to walk a lot to get between your home and work or wherever you're going. That's a big, big part of why people here are so much thinner than Americans. Having transport that takes you door-to-door without any significant walking is terrible for your health.
Tokyo has taxis and Ubers. I take them quite frequently when there, even though the public transit is amazing. The fact it's blatantly obvious that robotaxis make a ton of sense in even one of the most transit-friendly cities in the world shows how wrong the OP is.
If your neighbourhood is pleasant and walkable, you don't need to be dropped off at the door. In most cases, the key barrier to walkability is removing the cars.
However, for your "door to door" point, that's not desirable anyway. Even here in Tokyo, you have to walk a lot to get between your home and work or wherever you're going. That's a big, big part of why people here are so much thinner than Americans. Having transport that takes you door-to-door without any significant walking is terrible for your health.