Fat lot of good that logic would do Microsoft when they were deliberately gimping competitors.
In addition, I think Apple has so far somewhat successfully argued that they have reasons for restricting their ecosystem that aren't just a thinly veiled "because we want to crush competition". They argue that their devices are safer to use, and that allowing arbitrary software full access to the system would compromise that. Similarly, they limit third-party software from tracking you. They certainly aren't saints, and I disagree with a many of their choices (their app store cut could've decreased long ago, for one, and they're now adding ads into their own services) but they often seem like the only large corporation of their kind that even tries to have a set of beliefs and care about their users, and I think intent should matter.
I personally like that there's one popular ecosystem that has a particular perspective, and another competing popular ecosystem that has a totally different perspective. If you think all of the above is bullshit and Apple sucks, you're free to use Android and install exactly what you want on your phone. I've never really understood why folks are so adamant that this alternative should not be allowed to exist.
Apple is responsible for market damages inflicted onto software distribution by picking-and-choosing who gets to ship, and where their money goes. It is reflected in Apple's astronomical service margins, which unfairly reward them with even higher ROI than the iPhone hardware itself (!!!), somehow. It is seen in Apple's back-room negotiations with Amazon, Netflix, Google, Epic and X, where they use their de-facto power to force unfavorable distribution terms and draw up protection fees. It's present in their entitlement system, which gives Apple the option to artificially hamstring competing services that want to integrate with iOS. It's inherent to Apple's developer program, which has been used to revoke software signing certificates when Apple simply disagrees with a competitor.
Do we really think they deserve that money and power? It's not encouraging them to make smart choices.
In a fair market, I'd say that Apple can offer their services as an option. A factory-new iPhone could use all of Apple's offered services with a hardware-attested eFuse that says the device was never jailbroken. If a user wants to do foolish things like play Fallout: New Vegas with Proton, give Dropbox system-level integration a-la iCloud, use an updated RCS client instead of iMessage, install Fortnite or use a third-party app store, then Apple can give them that choice without endangering other people. It isn't impossible, they already do this with macOS, running the same XNU kernel, and with an architecturally indistinct ARM chip.
That would alleviate the market damages that Apple is responsible for, and create a positive pressure on iOS development to improve software-wise. Right now, Apple is being rewarded for extorting their competitors, pettily attacking consumers, blocking software features, stuffing ads[0] into first-party apps, and visually degrading iOS. They are clearly being protected from software alternatives that offer a less-invasive alternative to Apple's disgraceful OEM packins. Which is a shame, since Apple was historically not opposed to taking advantage of free software and making high-quality packin software that legitimately did compete against alternatives, like QuickTime and iTunes.
[0] https://www.pcmag.com/news/how-to-ditch-unsolicited-f1-ads-n...