As someone else wrote already, none of those are actually the reason Apple did it. I have asked Apple engineers and they don't even seem to know the reason beyond just... courage. Gotta make people buy Airpods somehow.
But here's to address your points:
1. Uh... no. They could have improved haptic feedback by working around this. Like you said, the battery is slightly bigger, but they could have kept the battery the same size and slightly reduced performance (like... 5%?) to account for battery life and kept the headphone jack around. Hell, the audio processing chips are still onboard for the speakers anyway, and those waste far more space than the headphone jack.
2. This is not a problem with most other phones that still have the jack. This is just you arguing for the sake of the argument.
3. Wrong. Samsung did it. OnePlus did it. Many other companies did it. Their phones are thinner than Apple's, even... so this is not an excuse.
4. Wrong. While bluetooth devices have improved leaps and bounds, Apple themselves still doesn't support the latest bluetooth tech with their iOS devices. Hell, they don't even have AptX with the iPhone/iPad/iPod. See:
https://darko.audio/2017/12/how-to-enable-aptx-hd-bluetooth-audio-on-your-iphone-ipad/
So yes, wireless audio products have improved. No,
they don't work at their best on Apple mobile devices. Apple devices are either 1 or 2 generations behind on the industry's best wireless techs. Android has had AptX support for a while and LDAC has been around since Android 8.0:
https://www.androidauthority.com/sony-ldac-codec-790690/
Apple still doesn't even support AptX despite their bluetooth chips being capable of it.
5. Okay, but why?
6. This is to address your point of buying something else other than Beats and Airpods: if something is not using the proprietary wireless tech that Apple devices are using, it'll sound like crap due to #4 above. This is not just a speculation based on voodoo stuffs like psycho-acoustic and such but it's just fact.
Apple is behind on supporting the latest wireless audio technology except for when it's their own proprietary shiz that nobody else has access to. If you want "good" wireless audio, you are obligated to buy either the Airpods or one of those Beats headphones.
And this is not even discussing anything about wireless vs wired but trust me, I have enough technical information to prove you WRONG that wireless tech has caught up as well.
At this point in time, or even 2-3 years down the line, there is absolutely ZERO excuse to remove the headphone jack.