Then somewhere around when people started to expect Windows on a computer the lifespans got quite a bit shorter, and that seemed to stick into the late 00s. And it's swung back the other direction now... my late 2011 MacBook Pro is good with current Mac OS or current Windows 10 installations, and is only being retired because its soldered-on discrete GPU has started to flake in a way that makes it unusable. (And a replacement motherboard would be stupid expensive.)
The advent of hard disks, and installable OS environments changed the model. Outside of zOS, and maybe IBMi, there simply aren't any OSs that actually have provided a fairly stable OS API over time. Even windows has decided they don't care about backwards compatibility despite the fact that for most purposes the core win32 API present in win2k provides basically everything needed to host the vast majority of modern applications. Games might be the exception but people forget the directX was an install-able component until MS decided to tie to to the OS with vista).
I can run 25-year-old Windows 3.1 applications on a 32-bit Windows 10 box and they work correctly. If I have upgraded to 64-bit, I am merely constrained to 22-year-old Windows 95 applications.
"Mobile devices will catch up and stagnate too, sadly."
Uh, if they catch up to my point, then they will still be useful at 5 - 7 years, thus the opposite of stagnant.
I believe the GP meant that the rapid progress of feature improvement will stagnate, which means older devices won't 'age' as quickly.
Plenty of people used 7-year-old computers in 2000.
My grandpa never got a smart phone. But he was never more than 5 years behind in Home computing well into his 80s.
Gadget nerds have criteria for computers which are not necessarily related to predictability, sturdiness, or fitness for a particular narrow purpose. Instead there is a mix of excitement about technology qua technology, new toys to experiment with, status signaling, etc., in addition to functional improvements for doing real work.
Not everyone shares a gadget nerd’s sensibilities. It’s fine for people to be happy watching TV on a 18" CRT, listening to music on a cassette player, reading paper books instead of a screen, rolling down their car windows with a little crank, playing card games instead of VR games, etc.
1: https://everymac.com/systems/apple/mac_classic/specs/mac_se....
Fixed that for you. Remember that every time you experience an unresponsive GUI anywhere, and that's the easy case.
Beyond that, parallelization is generally not easy.
E.g. Qualcomm SDM845 has 8 cores in total, 4 faster ones that are only used rarely, and 4 power efficient ones.
Also they offload increasing amount of work from less power efficient general-purpose CPUs to other on-chip hardware, DSPs (for many years), and now GPUs (marketing folks call them neural engines or AI chips).
Tell someone around 2000 that a 7ish year old PC would be adequate and you'd get laughed at. 1993 to 2000, for instance: You'd be comparing a Pentium at 60Mhz (some quick googling says 60Mhz was first hit this year) on the high end to a 1Ghz Athlon. Probably >20x real performance improvement (the clock alone is 16.7x).
Mobile devices will catch up and stagnate too, sadly.