Software similarity and market positioning don't really come into consideration once the role of gatekeeper has been established.
For me personally, all of the above is the cost and what I get is something I wasn't using and didn't miss (if I want to install things outside the walled garden, I use a my Mac not a mobile device).
Also, it costs the vendor to implement support for installing other software - resources the vendor could have spent on features I value, rather than features I don’t want. If only a government didn’t dictate to the vendor what it should do, stripping the vendor and the user of the power to decide for themselves.
And the resources needed to make an app installer are not nearly as high as you make it out to be because iOS already has the mechanism to install signed .ipas. All that's needed in theory is a check to disable signing (which they already have implemented in MacOS) and to add a few pages to the Settings app, which surely shouldn't be an issue for a tech company of Apple's size. And if you argue that it might break some spaghetti code then maybe that should be fixed anyways and it's doing them a favour.
As an anecdote myself, the main reason I haven't switched to a Galaxy S24 is because my Airpods work amazingly with my iPhone and Macbook, and my Apple Watch only works with iPhones. But very often I sorely miss having Termux, NewPipe, Tachiyomi, a non-gimped version of GBoard, Syncthing, a sensible launcher, and probably other things that I can't remember off the top of my head. I've decided that I value the Apple system more than the value I get from those apps but this regulation means I get to have my cake and eat it too.
Great! (Imagine having wallgardened Windows computer where you could not install whatever you want).
> This will mean a race to the bottom for iPad apps. Which, of course, means even more ads
iOS store is already at the bottom. Everything is with ads or subscription based. More ads won’t scare me because I won’t use app with any ads. If app offers one time purchase - I’ll buy it if I like it. Examples of apps I bought: Structured, Bobby, ArtStudio, MusicStudio.
> if I want to install things outside the walled garden, I use a my Mac not a mobile device
What if Apple decided you cannot install apps outdide off their App Store on a Mac neither? What would your “Apple-defending” argument be then? It’s NOT a far fetched idea. Microsoft tries it with Windows S Mode and they currently constantly threaten people when they download software from internet about how dangerous it may be, trying to scare people into using their store.
Again, you are presenting this as if it has only one side to it. I need a computer that has no walled garden for certain kinds of work. For other kinds of work I'm happy to know I can't break it. Even more important, I'm happy when my parents can't break the one I buy them.
>More ads won’t scare me because I won’t use app with any ads. If app offers one time purchase - I’ll buy it if I like it.
As long as such an option exists. But in a true race to the bottom situation, there may not be anyone willing to invest in developing an app and then selling for a one time purchase. One time purchase is a model that's nearly dead anyway.
>What if Apple decided you cannot install apps outdide off their App Store on a Mac neither?
This I wouldn't accept because I can't. It's a development machine for me. But an iPad is a consumption device, I need the thing to just always work.