Tell that to the people folding and flipping their Samsung phones (as well as writing notes with a digital pen).
The issue isn't the slowing of innovation, it's the stagnation of Apple's products. The new iPhones aren't discernably different from the model before it. More importantly, they fail to even integrate innovations that have been around for years now: under-display (or even power button) fingerprint sensors, always-on displays (a software feature!), lack of a huge notch etc.
And while we're talking about the notch...that symbolises Apple's stagnation more than anything. That abomination has now been there for 4 years and 6 iPhone iterations (X, XS, XR, 11, 12, 13). This year, they've slightly shortened the width while making it taller - and adding nothing to the notification area. Jobs must be spinning.