Points 1-3 has not happened to me, or if it has so rarely I can't remember. Point 4 has happened, though I've since set my phone to prefer cellular, which to a large extent mitigates this.
Point 5 I experience a variant of. My phone is set to not connect to open/random AP's, so I don't have directly the issue mentioned. Rather I see the phone clinging on to a known AP for too long, where switching to cellular would be better.
For example when I'm on my way home, I want to check the real-time bus schedule. By the time I've loaded up the app, I'm on the outskirts of the wifi AP's range. So for a minute or so I'm without any internet while my phone tries to get in touch with the AP before finally giving up.
Ideally my phone should have noticed that the range to the AP is declining steadily and that I have good cellular coverage, so it should have switched proactively when the wifi signal gets very low.
Overall though, both calls and internet just works for me.
You can also turn on some developer settings; e.g. mobile data always on (even with WiFi turned on).
Can't say if Apple got this right.
Absolutely nobody buying phones care about the items you listed, unfortunately.