If they are transparent about what they're doing, then it's not the same case I was talking about.
I can't see Apple saying "Well, on advice of our lawyers we can't actually explain our corporate structure to you." Is it a secret that they have a corporate entity in Ireland, is it a secret what they do with it? Or is it public knowledge that they don't hide?
So I wouldn't describe secret ownership structures as a thing "most every company out there does." But I'm not going to say Apple doesn't do unethical things. (Also is Apple even a trusted root CA for mozilla or microsoft browsers?)
I think non-transparency is an even higher level of problem for a CA. Secrecy about your corporate structure does not seem okay for a CA -- we need to know who they are and who controls them, non-negotiably. Secrecy of corporate structure does not seem like a thing most every company (or every CA) out there does.
But it's quite possible Apple should _not_ be trusted to "run the entire mobile ecosystem" that uses Apple products. You can make that argument. And we can talk about what the heck any of us can do about it individually or collectively if so. That's a different question than who should be allowed as a trusted CA root, or who Mozilla or Microsoft should allow as a trusted CA root.
When you say "that underpins all of this in the first place", I'm not sure what you mean; Mozilla and Microsoft trusted CA roots effect people who aren't doing anything with Apple products, Apple does not in fact "underpin" the entire SSL CA system in the first place. I don't know what to do about the Apple ecosystem if Apple can't be trusted, but I support Mozilla, Microsoft, or anyone else removing trusted CA roots belonging to companies with secretive corporate structures, ownership, or governance. All of this can be true. Apple doing unethical things doesn't mean mozilla or microsoft should allow a trusted root CA with secretive corporate ownership structure.