Alt Fuel car tax credit a good way forward?

Is an Alt Fuel or high fuel mileage car tax credit a good way forward to a cleaner environment?

I mean, it would incentivize ZEV purchases & create more competition in the auto manufacturing sector thus creating a stronger economy & product options with this stronger demand. In addition to taking larger gas auto off the street.

I know it's too much of a simplification but what am I missing here?

We are already giving credit to ppl buying water heaters & window sealants.