The Ford model shown has been oversimplified to the point of absurdity by using only one industry. The real economy is about flows between multiple sectors. Who's buying bread? Do they have enough disposable income to buy packaged bread or just flour to bake at home? If there's a packaged bread industry, does it become robust enough to justify buying delivery trucks from Ford?

On the other hand, on a much broader scale, the planet itself is a closed economic loop. There's a finite amount of resources and we're all just cycling most of them around back and forth.

Arguably, a significant amount of "growth" has come from taking resources that formerly were not "on the books" and putting them on. The silver in the New World wasn't in (Western) ledgers until the 1500s, the oil under the Middle East was just goo until the late 1800s. The uranium ore in your backyard suddenly got a lot more interesting after 1940.

New value can come from inventing new and useful applications for existing resources or by finding new external inputs (maybe capturing some of that radiation the giant fusion sphere overhead is blasting in our direction).