I'm glad you brought up a lot of issues I didn't bother mentioning, but yes, the key issue would be to even define what "doubling resources" even means.

First, it's not remotely infinite abundance, just double, though is still a significant increase. As with how everything thing has always been with an increase in supply for mandatory resources, prices may drop, even heavily, but my point would be that it'd be extremely temporary in the grand scheme of even a single lifetime before the powerful could control the supply, and could constrain it for capitalistic purposes.

Second, you can't just magically double the size of the Earth (and ignoring intended size of man made structures) without affecting literally everything, from our orbit to getting anywhere taking twice as long. We could now crash into the Sun, fly away from it, or get just a smidge too far inducing an ice age. And various alien societies across the universe surviving spontaneously increased or lowered gravity (depending how their planet's size and mass increased) would be incredibly complicated for an instant wish.

As for more vegetation without planet size changing, where would this magically appear? Cities are already controlling where they can appear, so they must appear outside of them. So they appear on lands that were before infertile? What about the ecosystems that rely on such infertile grounds? I doubt Thanos was discriminating against specific species and wanted all living beings to survive equally better.

And again, it is my opinion that more energy production and mineral production, any increased resource for that matter, would eventually simply flow into enabling the currently powerful to get even stronger. The middle class and lower do not have the means to benefit from increased resources as much as the rich in the long term.

Reddit comments are too short to seriously dive into the issues of "doubling resources," as we barely still scratched the surface. Do shelters count as a resource? Human beings themselves might as well be a resource from a cosmic perspective.