Smartphones ate the world, and they ate the majority of profit in the space. We are now 20 years on and the software is no longer driving the urgency of the hardware upgrade cycle it used to. Apple gets the majority of its revenue from iPhones and related services. Note that services category includes all sorts of App Store extortion payment stuff that they are slowly losing court cases over.
iPhones are so big for them, no other product category created since is even in the same order of magnitude. Partially I think thats on Apple, but I look across the consumer electronics space and don't really see anything new categories they aren't already dominating anyway (tablet, smart watches, etc).
One "moat" they probably do have is that in the US at least, theres not a lot of other physical retailers to go try out consumer electronics. 20+ years ago Apple Store were filled with 3rd party products, now its all Apple everything.