Public transit simply can't take you everywhere. Even when I e lived in areas with dense bus routes, how one would get to a stop was often a question. Buses are relatively slow and impede traffic, especially in larger cities.
More trains would be nice, but they share many issues with buses, including the fact that they become de facto homeless and mental health shelters on wheels. The only place where I have lived where this wasn't a problem was New Zealand, and that was 18 years ago, so I don't know if that's still the case. I always give up on public transit after seeing enough acts of human degradation and fights breaking out. Let's not forget the smell.
Cars and self driving tech will always have an edge over public transit. We might as well not waste too much time on public transit, but make sure it is adequate while making car-driving more sustainable.
In fact, I would rather prioritize making cities bikeable and walkable more expanding bus service. For some cities it's pretty much too late, but for ones that are kind of spread out there is no reason why there can't be dedicated bikeways.