Now I agree we need to do something but it'll just end up being an extra tax that will affect the poor more than others. If we don't tax everyone than it defeats the purpose of using taxes to drive behaviors. So we can't subsidize because that defeats the goal.
If on-street parking is crucial to the well-being of humanity, then we can absolutely subsidize it for lower-income people, just as we do for so many other things we've deemed critical. It's as simple as issuing a prox card that results in free or lower-cost parking. With a centrally managed parking system capable of dynamic pricing, there is no barrier to this strategy.
Finally, the whole purpose of using taxes to drive behaviors is that you're not taxing the people who don't engage in the behavior. That's how it works.