Building a city wrong doesn't mean "alternative forms of transport aren't very viable;" it means the city was built wrong and that must be corrected.

And make no mistake, that is very viable: the Netherlands already did it (it was not always like that: it was rebuilt for cars after WWII and then rebuilt again starting in the 1970s when they realized they'd fucked up). Paris is doing it right now. It is not actually hard, and it is not actually expensive -- at least not compared to the long-term societal costs of continuing car-dependency.

because everything was designed from the beginning with cars in mind.

This is a straight-up lie, BTW. All the cities -- including "newer" sunbelt ones, like LA or Houston or Atlanta -- were in fact built for walking and streetcars first, and then demolished to accommodate cars.