I have a 5 year old iPhone running iOS 16 which is snappier than most Android phones out of the box. The only problem I have is that it’s extremely aggressive at killing backgrounded apps due to the tiny amount of RAM and no swap.

However, it isn’t surprising or malicious for Apple to optimise their software for modern hardware. They still seem to do a significantly better job supporting old hardware than anyone else.

Perhaps some components in your phone are dying? If you go into Battery settings, has Peak Performance Capability been reduced?

1) You always need to wait a two or day before assessing performance. Often the Spotlight index is being rebuilt.

2) Nobody should ever evaluate anything on a .0 release. Wait a few point releases.

3) I've found the last few iOS/OSX releases to have better performance as their moved to pushing services based revenue.

Safari seems a bit faster to me