It's not that they haven't sorted this out, it's that they intentionally
broke it. S3 sleep was a solved problem all the way back in the Windows XP days.
The problem is that S3 sleep means the machine is actually sleeping, and short of timers being set ahead of time or explicit wake events by PCI devices, the machine is unable to think which means it can't do important things like download ads^W suggestions or similar. It's technically possible to do Wake-on-WLAN/WWAN but would require moving a ton of logic to the WAN card (it would need an entire network and app stack in order to maintain high-level TLS/etc connections with the various sync servers autonomously and wake the host when something new comes in) and in practice nobody bothered to do it because it's just not actually solving any problem the users care about - even when useful data is being fetched, it turns out that in practice nobody minds waiting 5 seconds for their Outlook to refresh.
Microsoft's "solution" however was to simply remove S3 sleep, so now the machine is incapable of it and is constantly in S0 (powered on state) and it's up to the OS to ensure nothing resource-hungry is running so that the CPU can actually enter its low-power states. This might be doable on an OS built from scratch (it's after all what all smartphones do successfully), but not with Windows if they want to preserve backwards compatibility with the PC we know and love, so in the end you get machines that have the risk of overheating & draining their whole battery while "sleeping"... but hey at least when it works your ads are up to date, progress I guess.