Also good luck getting reasonable (or any) cab service outside of Manhattan and NW Brooklyn. It was even worse pre rideshare days. Those are the areas that would need something like rideshare more since they're both less dense with less expansive public transit.

I don't know if private transport is ultimately unsustainable. That's something people much smarter than me will have to figure out how to measure. But I do know rideshare is objectively a better product for consumers across the board than the services it replaced.