I think the problem is non-orthogonality. So many choices are bundled together, and you have to decide everything at once, instead of taking it one at a time. For a MacBook, back when the line was really simple, you'd pick a size, then pick a speed, pick storage, etc., more or less independently. All you had to control for at each stage was cost. iPhones were even simpler: pick a storage size and you're done.
Now, things are bundled together. If you choose an iPhone screen size first, you're implicitly choosing camera quality, materials, speed, fingerprint recognition, and such things all at once. If you like a plastic case (some people do!) then 4" is your only choice. If you want the best camera, you have to get a 5.5" phone even if that doesn't fit in your pocket. If you're buying a MacBook, you have to optimize ports, weight, speed, fancy new haptic trackpad, and other such things all at once.
Compared to other manufacturers, Apple is still doing pretty well here. But it's still considerably worse than it used to be.
