I think you are being unnecessarily defeatist. Cities can’t be redesigned from the ground up, but at the same time we’ve seen that investment into roads can’t fix traffic in cities once they reach a certain population and density.

The first thing we should do is target development. For example, planning laws should require new development (suburbs etc.) to be built around some kind of transit (ideally rail). Zoning should always be mixed - for example it should always be permissible to have at least small apartment blocks, groups of townhouses (like row houses), and small shops and cafes in suburbs. The idea of mandating areas be dedicated to only detached single family dwellings should be consigned to the dustbin of history.

There’s just so much like that that can be started right now. But we don’t - we just keep making the same mistakes and things get worse.