The world could run on older hardware if software optimization was a priority

Let's keep the CPU efficiency golf to Zachtronics games, please.

I/O is almost always the main bottleneck. I swear to god 99% of developers out there only know how to measure cpu cycles of their code so that's the only thing they optimize for. Call me after you've seen your jobs on your k8s clusters get slow because all of your jobs are inefficiently using local disk and wasting cycles waiting in queue for reads/writes. Or your DB replication slows down to the point that you have to choose between breaking the mirror and stop making money.

And older hardware consumes more power. That's the main driving factor between server hardware upgrades because you can fit more compute into your datacenter.

I agree with Carmack's assessment here, but most people reading are taking the wrong message away with them.