I think you're putting business on a pedestal.
Every other mobile manufacturer can match Apple on hardware.
Apple's point of difference is the software.
But back to your point, Cook does not have a hard task if all he is going to do is keep the company within a set of safe boundaries.
We've all heard the rhetoric that there are exciting Apple products in the pipeline for years now. What were they? A smart speaker? A watch? Something we haven't seen yet?
IBM was huge. Microsoft were huge. At some point in time these companies, and others, were unstoppable.
Repeating what worked in the past as an approach for future success will eventually stop working at some point. It always does.
You mean the watch that sold 25 million in 2 years of full world wide availability... And generated 10-12 billion dollars in that time taking the whole market. Yeah, they probably missed that boat huh!. Any day, someone will produce something competitive... Any day.
Or the Airpods which basically are a runaway success and can be seen everywhere now and will be a pretty good platform for future wearables.
As for the homepod (first real time self adjusting speakers that's even in the ballpark of its current price), lets see how this Christmas season turns out and we'll see who has the last laugh on that one too.
Any of those things are very different from what anyone else is offering and would be considered monster successes if anyone else did it. Not even talking about Face ID which itself has many possibilities once it's full AR possibilities are exploited.
Apple has a closed pipeline unlike say Google. That's always been the case in the last 15 years; it drives analysts and seemingly people like you crazy.
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I think you're doing the opposite, you're thinking software alone is all. Apple's strength is in being the bridge that connects processing devices and components together to make user's life better.
So, Apple is a systems integration of: components and tech; ecosystem devices; outside environment, company.
The Software, especially the systems level one, is the glue that enable Apple's devices help their client/components best optimize themselves to their context. To get that glue done in the best way possible; they've decided to own the stack; to put some of the "software" into custom silicon they designed themselves.
That's something not many are doing. Why? Because it's a very expensive, very pointed expertise to have and deploy in house. So, it's not software, or hardware, it's something else; being able to remove, if needed, the obstacle that come from buying all your hardware off the rack by creating your own.
Other companies can't match Apple in systems integration, which is just the internal to the device extension of the ecosystem. Nobody marries software and hardware better than Apple.
Apple aims to marry the "HW" that is the real world environment to its devices/sw ecosystem. Bringing in the whole world into its ecosystem.
IBM was very big for many many decades btw, a lot longer than Apple has been on top, from the late 1950s to early 1990s; a lot longer than Microsoft ever was.
IBM's though was never really consumer electronics and that's why they couldn't take the same turn that Apple took. The other kink in its armor appeared by the rise of microprocessors throughout the 1970s and the big change in computing architecture that this allowed. They still might have won if not for a few key decisions; so, using it or the few companies that were on top, is anecdotal at best.
They all have their own reasons for not being there and whenever it happens to Apple, it will be understandable in retrospect why it happened.
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Yes, Apple is vulnerable in the long run. Even the Roman Empire didn't last eternally (though they lasted in one form for 1400 years which isn't bad ;-). I truly don't think Apple will last 1400 years

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