My analogy would be: "America would be so much better if everyone voted." It's not wrong, it's incomplete, we really want everyone to fully understand the issues and then vote. Likewise, a public transit system alone won't make a city better, but a well-planned and executed one will.

I don't think it's unreasonable to say that if Elon successfully revolutionizes boring technology, it might be better to use it on a really good public transit system. And it's an especially important conversation if his fully realized tunnel network would make a later subway system more difficult/impossible even if people wanted one.

But it has already been proven to work, in Tokyo and Hong Kong and Shanghai and London and Paris and countless other cities, countless other times.