This is bad on a mobile operating system. I had the displeasure of trying a device running Android's default UIs a few weeks ago: it felt like a Fisher-Price toy. Apple's model of organization is better in every way.
Sometimes it seems like Apple's lack of choice is the primary reason people prefer Apple.
A lot of times, it's easier to write something like a narrative when you're working within certain rules. Or to design a powerpoint when you're given a corporate style guide.
Starting from scratch is difficult because it doesn't give any ideas to bounce off of. And with something like a smartphone - which users need constantly, but never seem to have the time to configure - any half-hearted configuration by the average user is going to benefit dramatically by having basic rules in place.
For power users - like all of us on Hacker News - sometimes the blank-slate approach is preferable, but there's nothing wrong for liking Apple because of the lack of choice.
But anyway the reason Apple doesn't allow for customisation of the home screen is because it adds complexity. And given they are trying to sell to people who are computer and technology illiterate you don't want complexity.
iOS has gotten already too complex that I don't think avoiding complexity is a strong enough reason for not offering home screen customization.
I always wonder what iOS 13 would look like if they didn't dump iOS 6's design so thoroughly.