I had my iPhone XR (bought 2019) until last year. At that point an upgrade made it so slow it was barely usable, while the lack of further updates made it impossible to install or upgrade apps after the device and OS went EOL.
the xr performance/hardware is still very fine when you look at it on paper, very annoying forced obsolescence for no actual reason
A lot of times, it’s the battery age causing this issue though. Once the total battery capacity drops below 80% performance just collapses. Luckily, battery replacements aren’t totally crazy expensive and end up being worth it a lot of the time.
My wife's SE 2020 is on its third battery. It was fine until she accidentally upgraded to iOS 26, but now it's a mega lagfest. Apple's refusal to allow OS downgrades is infuriating, because it's still a perfectly adequate device otherwise.
I’m not convinced that was the issue in this case, as the battery still lasted all day with my normal usage, and the phone became slow overnight after a major OS upgrade.