I’ve had the same experience. I had a 6s and an XR, and they both slowed down tremendously overnight after iOS updates (not the same one, 6s happened a few years before). Also, the update for the 6s that caused performance issues also removed/made redundant a lot of the OS features that made use of 3D Touch, because the newer phones didn’t have it anymore. For the 6s, I know it wasn’t a battery issue; I replaced that battery, and it didn’t fix them.
For a minute, battery replacements or repairs weren’t even a reasonable option, with how repair-unfriendly their phones had gotten. But afaik they’ve improved in that regard, providing official tools, parts and guidance. Also, you can call them to have them activate the Face ID module if you replace a screen, which is a big win for right-to-repair. Props to them for that!
I’ve had the same experience. I had a 6s and an XR, and they both slowed down tremendously overnight after iOS updates (not the same one, 6s happened a few years before). Also, the update for the 6s that caused performance issues also removed/made redundant a lot of the OS features that made use of 3D Touch, because the newer phones didn’t have it anymore. For the 6s, I know it wasn’t a battery issue; I replaced that battery, and it didn’t fix them.
For a minute, battery replacements or repairs weren’t even a reasonable option, with how repair-unfriendly their phones had gotten. But afaik they’ve improved in that regard, providing official tools, parts and guidance. Also, you can call them to have them activate the Face ID module if you replace a screen, which is a big win for right-to-repair. Props to them for that!