That's just it; that's clearly not the case.
You're downplaying the experience of millions of other iOS users, many of which are just as acutely aware of the performance of their devices as you are.
You're also overlooking the fact that thousands of people beta tested this release of iOS for weeks before it was ever released to the public.
I personally see none of the issues you do; that doesn't make my experience any more important than yours, yet it is a data point as if it were an obvious issue in iOS 16.3, I'd see it too.
None of this is meant to downplay your experience; rather if it were iOS doing something obviously wrong there would be a lot more people complaining of this issue both here and around the world. There are other factors here, either a combination of apps on your device, your cellular and/or Wi-Fi network, etc.
In the end, the bottom line is unless you haven't opened a case with Apple Support directly, you've done all you can do if you don't want to investigate what on your device could be causing your issues.