Genuinely, why have an iPhone in the first place if you want this?
I still have my linux desktop when I want to tinker.
There is no single provider that does all of that combined as good as apple.
..."until I want to do something that the default Apple behavior does not do."
To oversimplify, it's like saying "you can do these 10 things and they're guaranteed to work". On some platforms, you can do things 11-20 as well, but there's a chance they may not work as desired. This may still be preferable to a total inability to go past the first 10 due to restrictions.
I find that a lot of computing devices work fine out of the box if you use them exactly the way the included first-party options were tested to work. It's gotten to the point where I'm less concerned about how nicely they succeed at the "common" things than how well I can deal with them when they "fail" (to do the thing I want them to do).
I appreciate easy and convenient as much as the next person, but if I have to choose between "must install app or change configuration to do what I need" and "nope, you can't do that", I'll take the former.
But for what it's worth I personally had a very good customer service experience with them. I had a laptop where I couldn't enable the TPM anymore and they asked me to ship it to them to look at it and replaced it with a newer model. That was in Germany though and just one case.
It's a night and day difference with mac.
I even have realtime watch complications which no shipping app can have because of apple restrictions - developer mode lets you push complication updates realtime if you want.
I'll probably consider something more open next time I buy but just pointing out that right now with a developer account you're not actually _that_ restricted on iOS, the experience is better than you might think if you're making an app you never intend to ship.
I am not arguing Apple's restrictions are a good thing, if I were in charge I would in fact make allowing installing your own software on your own device a legal requirement of selling hardware, yet here we are.