From a CPU perspective, they still are:
https://www.anandtech.com/show/13392/the-iphone-xs-xs-max-re...
(for the rest of the features, that's indeed debatable)
Fun fact: Samsung made the chip for the first iPhone. Steve Jobs was so dissatisfied with the experience that Apple bought PA Semi to design the chips in-house.
I thought PA Semi's specialty was in power management and many didn't consider the acquisition a success as most key figures left the company not too long after the acquisition. Are you sure that Apple actually designed the SOC in-house? Wasn't it Intrinsity, Samsung's collaborator, that co-developed Samsung's Hummingbird core (also used in Apple's A4) to compete with Qualcomm's APs and go beyond the 1Ghz barrier, changed the game?
I always thought the Hummingbird was the breakthrough that made the A chips competitive -- Apple bought Intrinsity afterward.
Not that I'm against extra horse power, we'll find a use for it. But we're in "desktop land", almost, for smartphone CPUs. They're good enough.
The real smartphone battles now are in camera quality, gaming oomph and battery usage.
I think it's been longer. I'm on a non-flagship from last year, watching YouTube in PiP mode while writing this comment. Way more than necessary power for causing use.
Probably also a case of modest needs, but still.
When you buy the highend they become average in a few years which is completely useable. However, low end phones quickly fall behind the curve and only keep dropping.
Now, that’s not to say the phone will physically last longer. Just that having headroom becomes more noticeable over time.