Unless you can come up with something better then what I presented, the burden is on you.
Cars do get better gas mileage then 30 years ago, and it’s absurd to think otherwise. A typical late-70’s GM V8 car was getting about 10-12 mpg. Additionally cars pollute much less today, and have hugely better performance, so perhaps your “mileage is about the same” isn’t quite apples-to-apples.
Engine performance improvements have largely gone towards HP and torque, and not MPG, because that sells cars. If you don’t believe me, go look at 0-60 times for the average car then, versus now.
And you still fail Logic 101. There is never a burden to prove a negative, which you are still demanding.
One word which never comes up in discussions of cars is “weight”. The small cars of today are generally around a thousand pounds heavier than those of 1965. Really hard to like that in our present age of miracle materials.