In theory, you can power a big car on responsibly sourced fuel. In reality, selling millions of big cars is a huge problem, because of course people will understandably put in the cheap, ubiquitous fuel for which they're not covering externalities.
This saying is not suitable here because unsustainable technology isn't good. It's simply not worth the cost and we are borrowing from the future.
If the venture would be unprofitable up until the point when it would be sustainable would we still push money into it?
I say we should treat any venture that is unsustainable the same way we treat those that are unprofitable. But we don't. We allow unsustainable ventures to carry on without ever becoming sustainable. Which means that it is constantly borrowing (stealing) means from everyone else.
Biofuels doesn't necessarily mean subsidized corn fields... for example, algae and bacteria grown under specialized LEDs powered by renewable energy are another path forward.
Perfect is the enemy of the good. We can research supersonic jets in addition to better electric storage and propulsion systems.