>Classical economics expects growth, forever. Many scientists have complained that this is absurd, and untested, and unprovable, given the laws of thermodynamics and a finite planet. Indeed any observer can see today that our population requirements are bumping up against resource limits and global warming.

It's not absurd at all because economic models never claimed to be able to predict anything at the time scale where the laws of thermodynamics become the upper limit to growth.

We're hitting resource limits and global warming but all of that has solutions. We could do a full turn towards renewable energy sources right now and economies would still grow. They just wouldn't grow as much, so short term greed doesn't allow it.

None of that is preventing growth. Quite the opposite, right now growth rates are a source of the problem, not a consequence.

>Ancient empires grew until they exhausted local resources and then collapsed

This didn't really happen very often. Ancient empires didn't really have the production capacity to exhaust big resource reserves.

The more common case is that ancient empires collapsed because the resources themselves decreased due to outside factors. War, disease, drought, floods, etc...

You can advocate for slow and sustainable growth all you want. No one's going to say it's not a worthy cause. However, a system that works contrary to human nature is bound to fail and therefore pointless. The solution lies in playing along with human nature, and not against it. Research leads to technological advances that make sustainable energy sources cheaper, and therefore better for both growth and sustainability. Vote for that.