Software development in most areas (e.g. Windows, games) did not focus on using resources more efficiently because new Windows versions and games drive hardware sales. There is little incentive for developers. The generational improvements in speed, graphics etc. have become minimal. E.g. Pcie 3.0 vs. 4.0 SSD's are not meaningfully slower in day to day use.
Discussion
I understand this argument for Apple, but less so for Microsoft. The revenue they get from OEM Windows licenses is peanuts whereas prior to W10 they got away with charging min $100 for consumer software updates.
Surely this gives them incentive to keep Windows running on existing hardware?
Think it's a matter of perspective. Linux for example runs on very old hardware well.
MS Windows just needs more resources in my experience and MS or OEM do not support older hardware anylonger (e.g. drivers, windiws versions). Hence, people got used to buying a new PC every so often so the softwsre they use continues working well.
Apple is kind of a special case as they own hsrdware and software. They control "obselesence".
The case of linux shows that leaner OS are key for performance and efficiency irrespective of the hardware.