If you re-read the first few chapters of The Innovator’s Dilemma and you insert “Apple” every time Clayton Christensen mentions “a company,” a certain picture emerges: Apple is a company on the verge of being disrupted, and the next great idea in tech and consumer electronics will not materialize from within the walls of its Cupertino spaceship.

The Innovator’s Dilemma, of course, is about the trap that successful companies fall into time and time again. They’re well managed, they’re responsive to their customers, and they’re market leaders. And yet, despite doing everything right, they fail to see the next wave of innovation coming, they get disrupted, and they ultimately fail.

In the case of Apple, the company is trapped by its success, and that success is spelled “iPhone.”

Take, for example, Christensen’s description of the principles of good management that inevitably lead to the downfall of successful companies: “that you should always listen to and respond to the needs of your best customers, and that you should focus investments on those innovations that promise the highest returns.”

Molly Wood (@mollywood) is an Ideas contributor at WIRED and the host and senior editor of Marketplace Tech, a daily national radio broadcast covering the business of technology. She has covered the tech industry at CNET, The New York Times, and in various print, television, digital and audio formats for nearly 20 years. (Ouch.)

Then think about the iPhone, which, despite some consumer-unfriendly advances like the lost headphone jack and ever-changing charging ports, has also been adjusted and tweaked and frozen by what customers want: bigger screens, great cameras, ease of use, and a consistent interface. And the bulk of Apple’s investment since 2007, when the iPhone came out, has been about maintaining, developing, and selling this one device.

In the last quarter of 2018, the iPhone accounted for $51 billion of Apple’s $84 billion in revenue. Its success, the economic halo around it, and its seeming invincibility since its launch have propelled Apple to heights few companies have ever imagined. But the device will also be its undoing.

Here’s what happens when you have a product that successful: You get comfortable. More accurately, you get protective. You don’t want to try anything new. The new things you do try have to be justified in the context of that precious jewel—the “core product.”

So even something like Apple’s Services segment—the brightest non-iPhone spot in its earnings lately—mostly consists of services that benefit the iPhone. It’s Apple Music, iTunes, iCloud—and although Apple doesn’t break out its numbers, the best estimate is that a third or more of its Services revenue is driven by the 30 percent cut it takes from … yep, apps downloaded from the App Store.

The other bright spot in the company's latest earnings report is its Wearables, Home, and Accessories category. Here again, Apple doesn’t break out the numbers, but the wearables part of that segment is where all the growth is, and that means Apple Watches. And you know what’s still tied nice and tight to the iPhone? Apple Watches.

Even Apple’s best-selling accessories are most likely AirPods, which had a meme-tastic holiday season and are, safe to say, used mostly in conjunction with iPhones. (I'd bet the rest of the accessories dollars are coming from dongles and hubs, since there is nary a spare port on the 2018 MacBook.) As for stand-alones, its smart speakers are reportedly great, but they're not putting a dent in Amazon or Google, by latest count. Apple TV, sure. Fine. But Roku shouldn’t have been embedded in a TV before Apple was.

And none of these efforts count as a serious attempt at diversification.

You may be tempted to argue that Apple is, in fact, working on other projects. The Apple acquisition rumors never cease; nor do the confident statements that the company definitely, absolutely, certainly has a magical innovation in the works that will spring full grown like Athena from the forehead of Zeus any day now. I’m here to say, I don’t think there’s a nascent warrior goddess hiding in there.

Witness Apple’s tottering half-steps into new markets that are unrelated to the iPhone: It was early with a voice assistant but has stalled behind Amazon and even Google Assistant. It wasn’t until last year that the company hired a bona fide machine-learning expert in John Giannandrea, former head of search and AI at Google—and he didn’t get put on the executive team until December 2018. That’s late.

There’s its half-hearted dabble in self-driving technology that was going to be a car, then became software, then became 200 people laid off. Its quailing decade-long attempt to build a streaming service would be sort of comical if there weren’t clearly so much money being thrown around, and so tentatively at that. Rumors of its launch go back as far as 2015, although now it’s supposed to launch in April—this time they mean it.