Even if our apps used resources better the adware will just use the free space.

Answer: there'd be far less software in the world, it would all be more archaic and less useful, and our phones and laptops would just sit at 2% utilization most of the time.

There's an opportunity cost to everything, including fussing over whether that value can be stored as an int instead of a double to save 8 bits of space. High level languages let developers express their feature and business logic faster, with fewer bugs, and much lower ongoing maintenance costs.

I fully concur. There's tons of really inefficient software out there that wastes resources just because for a long time, available resources grew fast enough to just keep using more of them without the net speed of an application slowing down. If we didn't have so many lazy SW devs, I suspect the reduction in needed CPU cycles would have a measurable positive effect on climate change.