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.