It used to be the case that if Apple wanted to build a walled garden / cathedral, then in order to compete in the hardware marketplace they had to provide software that didn't suck. You knew that if you bought an Apple product, there was reasonable assurance that everything was tightly integrated. If it wasn't, you'd go buy a market alternative (Android, PC). In my mind, this means that they spent a lot of time and dev resources (i.e. money) on their Frameworks. I think it showed. Time was spent on design. They focused on opening up capabilities "the right way."
Now that's pointless. If the iPhone is just an Android phone with a different coat of paint, then dev resources are going to be shifted to a place where Apple can distinguish themselves in the market, where they have platforms that they can control: Services.
Your argument essentially boils down to: If Apple doesn't get to do whatever they want without compromise, their execs get too discouraged and depressed to innovate. The obvious conclusion is that the only way we can enjoy the unrivaled genius of Apple is to give them a blank check to do whatever they want.
Every act of consumer protection and every form of pro-competitive regulation is twisted and exaggerated, no matter how insignificant it is to their bottom line or product functionality. The world is ending any time they don't get their way and when the world doesn't end, this decision becomes the scapegoat for all of their future faults, missteps, and bad performance. They can never do anything wrong and nothing is ever their fault, it's so so incredibly tiring to listen to this.
It's a terrible anti-feature and the only reason they're not being punished for it is because there aren't many alternatives to pick from.