Antitrust does not mean literal monopoly, and 57-70% share is certainly big enough to exert anti-competitive pressures, which are detailed in the antitrust suit. It's also not like the government is trying to break Apple into multiple companies, like Standard Oil.
Moreover, the author himself then goes on to detail for most of an article some of the ways that Apple doesn't play nicely with others (of which there are many many others) and how their own reasoning for why they need to be this way doesn't hold up (all those fake Sora apps), but then comes to the conclusion that it's not bad enough for him (who happens to be inside the Apple ecosystem). The author does not address people who are pressured to be in the Apple ecosystem (see teens & the green bubble), but just says they didn't feel any pressure.
He doesn't even seem against the EU restrictions, but he still, without listing any concrete repercussions, doesn't want the government to make choices for Apple.
Overall, it was a pretty unhelpful article to me, with a kinda odd stance of yes they do bad stuff but I like my iPhone so the government shouldn't try to make them play nicely.