I'm a reasonably-satisfied Android user, but Android is nearly as locked down as iOS. Sure, I can (and do) run "real" Firefox on my Pixel, and can (and do) side-load apps, but there are quite a few things I can't do.
For example, my Pixel 4 just fell out of Google's 3-year support period, so I no longer get security updates. I would be completely happy to run LineageOS or some other alternative that would extend the life of the phone with regular updates, but I can't if I still want to be able to use Google Pay and other apps that require the phone to pass SafetyNet. Those sorts of apps are a part of my day-to-day, so being unable to use them would be a showstopper. (I've read various things about tricking apps into believing the phone passes SafetyNet, but none of the methods seem particularly reliable, and for every user who says it works, there's another person who couldn't get it to work.)
So sure, it is technically possible for me to treat the phone as "open" and run whatever OS image on it I want, but then I become restricted in other ways as to what I can do on it. Maybe you don't care about being able to pay for things using your phone (etc.); that's fine. But I do, and I consider it a critical feature these days.
For example, my Pixel 4 just fell out of Google's 3-year support period, so I no longer get security updates. I would be completely happy to run LineageOS or some other alternative that would extend the life of the phone with regular updates, but I can't if I still want to be able to use Google Pay and other apps that require the phone to pass SafetyNet. Those sorts of apps are a part of my day-to-day, so being unable to use them would be a showstopper. (I've read various things about tricking apps into believing the phone passes SafetyNet, but none of the methods seem particularly reliable, and for every user who says it works, there's another person who couldn't get it to work.)
So sure, it is technically possible for me to treat the phone as "open" and run whatever OS image on it I want, but then I become restricted in other ways as to what I can do on it. Maybe you don't care about being able to pay for things using your phone (etc.); that's fine. But I do, and I consider it a critical feature these days.