It's nothing like a slam dunk case. In fact, it's an attempt by DOJ to stretch and redefine the edges of their rights under anti-trust rules.
It's also nothing like Microsoft -- Microsoft was a monopoly, full stop, in the 1990s. They were well over 90% of desktop market share in business, and likely close in consumer. And as 1990s era Microsoft employees will remind you if you ask them -- "there's nothing wrong with being a monopoly, only abusing your monopoly power". Forcing IE on people was considered abuse by the courts of the time, and even then was widely considered to be a result of a Clinton-era DOJ, e.g. politics were involved. As they are now, both progressive anti-big-tech politics, and bipartisan anti-consumer encryption politics.
Today there are hundreds of functional choices you could make for any sane definition of the product categories Apple is in. Mobile phone? Sure - from totally open Pinephone type systems to vanilla Android to stripped-down Android to ... Laptop? yep. Servers/Desktop? Please. Watches? Check.
Are there any major pieces of software that consumers must have that are locked to Apple, and that Apple is charging egregious rent on? Nope. Most Macbook airs are really just browser engines. As of 2020, about 50% of those macbook airs ran Google's chrome as their primary browser.
You might, like me, feel Apple's App store walled garden is on balance a net positive, leaving me with almost no worries related to upgrade problems, my family's phones being compromised by malware, etc, or you might like many others hate the controls, want to root your Android phone and install your own apks directly, and thus choose Android or some other unix-a-like-on-mobile -- more power to you.
What we've seen you won't get the US courts to do is conclude that Apple's huge user base and developer base, controlled through their App store, is somehow a 'public good' that needs to be given away to others that didn't pay to develop, build and market it -- that's pretty much settled. It's valuable, super valuable. It's a competitive moat. But it's not abuse of a monopoly position to have such a thing.