

Well, smaller cars are less of an issue on every metric. They take away less space…
Unless they’re kei cars in an area with special zoning laws mandating half-size parking spaces for them, all cars take up the same amount of space at rest: one parking space each.
In motion, the space cars take up is dominated by following distance, not the length of the vehicle itself, so small cars don’t meaningfully increase the capacity of the road either.
In other words, from an urban design/engineering perspective, all cars are effectively the same size. The only things that get considered separately are the really big vehicles, like firetrucks, buses, and 18-wheelers.
As for the other aspects: yes, small cars are better, but it’s a marginal gain rather than a transformational one. In this space, of all places, I prefer to focus on those transformational gains rather than preemptively compromising. Remember, a radical flank is always necessary in order to make the moderate position look moderate. You can’t shift the Overton window without demanding more than you expect to get.
There may be folks with some types of disabilities who benefit from using a drive thru, but there are also folks with other types of disabilities who can’t use a drive thru because they can’t drive and who are materially harmed by the lack of walkability drive-thrus cause.
In fact, considering that there’s nothing in the Americans with Disabilities Act that requires restaurants to have drive-thrus, and moreover that lawsuits regarding drive-thrus and people with disabilities tend to be almost universally about people who can’t use the drive-thru being forced to use it rather than the other way around, I’m very confident that my position isn’t ableist.
(And that’s considering your argument at face value, which is pretty charitable considering how often it’s made in bad faith.)