Every CPU cycle used by software, including an Operating System, depletes a limited pool of immediate resources.
If the same device and functionality I enjoy have not changed, then the room for concern arises.
When I think of planned obsolescence and sorta-unintentional performance regressions on desktop operating systems, I'm instantly brought to YouTube's Polymer website and UWP. Two complicated things but they largely only benefit the developers of the software and have not actually delivered any features. Google is a huge part of the desktop world and they're not so "external" as pabs3 says and to me it's just part of the software right to repair movement.
Now 14 suddenly isn't an option anymore. Exploits are still found and the only way to patch them seems to be to go to iOS 15.
Luckily the latest Nokia clamshell phones have good mobile broadband support and also support Telegram and Signal it seems. With the price difference between a brand new iPhone and a brand new Nokia clamshell I can also buy a really good camera and then I think I got it sorted mostly.
Banking apps have mechanisms to check if there's an update available and not give access unless you install it. You then can't install the app update unless the OS is sufficiently new.
There should be no right that barring some major security changes, that core functionality is not only impacted, but that added features impact performance or that a user should have the right to choose performance over features.
I reiterate my example, would it be ok with you if your car lost 100 hp or 20 mpg fuel economy over 5 years because there were things added to your car that weigh it down so much or due to a roughshod rebuilding of your engine every time you changed your oil?
It is really a clear case of fraud and destruction of property when, e.g., a phone becomes so laggy that it is unusable over 5 years solely due to updates that were imposed and required by manufacturers even if they try to justify it by adding things you did not request or need or want.
I am actually surprised that an enterprising technology aware lawfirm has not latched onto this issue. It seems to me to be a rather simple case of proving at the very least the negligence and willful destruction and degradation of others' property.
To simplify the concept, e.g., we are constantly told by phone makers that next-phone is N times faster/more powerful; so how is it that the phone I was told is 5 times more powerful than the predecessor, all the sudden lags when swiping between home/app screens or launching a dialer, a core functionality that hasn't changed in years and like it never did before?
At best, we are facing an immensely sloppy industry that damages our products and property through forced updates; at best.
Could you expand on this? Why wouldn't you want a machine that's not running spectre mitigations on your network?