Except for "I have to buy hardware", that's... just not true. Even buying the hardware can be circumvented but let's stay strictly legal here.
As OP said, it's unix, at least extremely unix-y so you don't have to learn apple specific languages. You can choose to do so for better integration to their system and vision and UI idioms (and should I say, macOS native applications are the BEST thought out applications you'll ever have the pleasure of using in user experience side). But whatever code you run in Linux will be trivially ported to macOS.
Learning a new OS is... I mean it is a new thing to learn but it isn't like you didn't learn the OS you are using at some point. Unless you think that there should be one and only one OS for the entire universe that everyone uses, this is an irrelevant point.
For the IDE, again, you don't have to, but you can choose to learn. Most popular IDEs natively work on macOS just fine, and you can just use your terminal like in any unix system, use your build scripts etc.
For macOS, you don't have to be compliant with anything, you can distribute your apps the old fashioned way. If you want to be in their dedicated store though, yeah they have rules. I think that makes sense.
For iOS, that store is the only way to distribute software and your points would make a bit more sense. But I actually am on the fence about the merit of the walled garden approach of iOS. Android ecosystem is a cesspool of malware. I can deal with malware on my computer. My computer has the resources etc. And computers are my job. But my mobile phone IMO has to run trusted code, I will happily delegate some standards to a central body as long as they manage it sufficiently well. When I install an app, I want to be sure that there are reasonable protections about what they can and can't access in my phone. I take my phone with me everywhere, it knows A LOT about me. I can't disassemble all binaries I use to make sure they aren't doing anything shady. Apple has automated tests for this stuff. I know it can't be bulletproof but it is something. They are fast to respond to exploits and they manage to keep their platform secure.
If a "free for all" device was popular, I'd still manage. I'd just have to be EXTRA EXTRA paranoid about what I install in my phone and it would decrease my productivity and quality of life quite a bit. That I can manage. But the whole ecosystem would be A LOT less secure. Not many people would exercise discipline. Viruses, malware, rootkits everywhere, billions of people carrying them in their pockets everywhere. My inclination right now is that that would be a worse deal right now for the world. While Centralisation and corporate power is something I generally despise, in this case (mobile OS, walled garden, corporate control over what apps can and can't do on their platform), I think can see the merit as long as they don't majorly screw it up.