First off apologies for replying to the second part of your argument separately. Life, as they say, got in the way.
Let me also say that I really appreciate your civil and thoughtful contributions, even though or probably because I don't always agree with you.
The thing is - Apple made the conscious decision to give up market share in exchange for profits when they decided on an integrated product approach (where they control the hardware, the OS and the services that run on the device). I have gone through well over a decade of naysayers criticising Apple's business model and claiming that it was flawed, that they needed to offer cheaper smartphones, that they needed to allow sideloading and be more open like Android. Apple instead went on to do the direct opposite of what the critics said, history has shown that they made the right call (having commanded the lion's share of the industry's profits despite having like 20% worldwide market share), and the Epic / Fortnite saga demonstrated that users don't really hate closed, sandboxed ecosystems.
While I don't disagree with your overall argument, I'm not sure why it should matter in the context of the DMA.
The primary concern aren't closed ecosystems per so as shown by many, including yourself, pointing at consoles being able to continue operating a closed and sandboxed ecosystem.
I don't want to engage in too much hyperbole, but I think we can agree that smartphones have come quite a long way from the mid-2000s, and so have all forms of digital commerce. If someone had told me in 2004 that 20 years later I would do most of my everyday personal computing on my phone, I would have been sceptical at least, now Apple and Google basically control access to consumers in a way Microsoft never did.
From Apple's point of view it must of course be frustrating to have your business model disrupted despite (mostly) sticking to legal requirements, but when the world changes, the law must change with it. What is the alternative?
Apple did everything right (I maintain that many users chose the iPhone in part because of its locked down nature, not in spite of it), and that is why I still cannot really accept how the narrative is shifting to one where users are trapped in a walled garden and only government intervention can save us from our own poor choices.
That's really my biggest bugbear here.
In terms of economic success, Apple clearly made the right decisions. I just don't believe its locked down nature is influencing anyone but a comparably small number of users. I bet that if you surveyed a representative group of iPhone users, 'because I can only buy apps from the App Store' would not be a major driver.
I find it hard to not argue that the walled garden 'traps' users. Apple says at much itself in all the materials that were disclosed in legal proceedings.
Of course you're not trapped in the strictest sense of the term, but network effects and feature lock in are real, even if you can of course leave at any time.
It's not just Apple, of course, and that's what is being missed here so often in conversations about the DMA. This is not just about Apple. In many ways it isn't even primarily about Apple, even if MacRumors coverage may suggest otherwise. Think WhatsApp, for example, and how dominant it is in Europe. It's basically impossible for anyone to compete unless interoperability is enforced.
In any case, I think the DMA is a good idea to keep the door open to competition and at least have a theoretical option to not be beholden to just two companies when it comes to which software we can use on our devices. More than lower prices, which may or may not happen, this is the primary win for me. Successful competitors may emerge, they may not, but at least there's a chance.