Low-level power savings (s3 sleep) and magic packet (Wake-on-LAN) have been a standard since the late 90s. Getting a Linux OS that actually delivers these standardized power features is now a 20+ year old bug. I can only imagine the amount of energy that would have been saved if this bug was properly fixed 25 years ago. With solid-state tech becoming cheaper every day, I now expect nobody will make an "it just works" OS that has both sleep and wake working on-demand. Globally, the HDDs will simply continue to spin until there are none.
Who pays for Linux development? Either companies for servers or embedded Linux. Servers don't sleep. Embedded might sleep, but it's not PC hardware, so it needs completely different power management features.
Nobody is paying for Linux on average PC hardware, that's why 20 year old bugs are not fixed.
