It’s not truth. It’s a form of techno-libertarianism bordering on religion. I can’t find a single working scientist in any relevant field who believes this claim. Most scientists believe we are on our way out, along with the biosphere we’ve destroyed.
Also, let's wave the magic wand and make all cars non-polluting during operation (not even dust from the brake rotors).
Where do the natural materials which are used to make the car come from?
What about the materials which make the road network that the cars drive on?
What about the natural environments which get turned into suburbs because mobility is "easy"?
How much of the surface of the earth is co-opted for human-dominated and human-determined?
Jevons Paradox also comes into play.
What I mean is, e.g., when the cost of energy drops people's energy bills in general do not go down, the have warmer homes. That has been known for a while. But is it still true if everybody can keep their houses at 21 degrees permanently? At thatr point does a reduction in energy costs reduce their bills or do they find something else to spend the energy on?
As a % of the population, I don't know how many have those traits - 10%? 1%? - but with a population also numbered in billions, "enough to totally screw the planet" is a reasonable guess.
Besides, considering that we are living on a finite world, we don’t need to merely decouple economy from materials, because any use at all will at some point exhaust available resources. Sure, we can say “fuck everything, I’m going to keep going on as usual because in 100 years I’ll be dead and they’ll have that one wonderful technological panacea that will change everything (be it Mars colonisation, asteroid mining, or anything else)”. I don’t know how to call that attitude except for “techno-libertarian dogmatism”.