I do get the original posters point.
There are some limits we've reached or are close to in terms of the perfection of the current design for iPhones. You could see the pixels in the first iPhone. This stopped around iPhone 4 and as the screen tech improved and the resolution and brilliance is now so high/great that there's not much more you could do to make things look better to the average person's eyes. We have a 120hz display. We're at the point where humans eyes aren't good enough to benefit from further improvements.
There was a time when I had to charge my phone multiple times a day, when I had to keep brightness down low and turn off a load of stuff running in the background to try to keep decent enough battery life. That finally stopped around the iPhone 8 for me and is no longer an issue. Sure we'll get better battery tech, better power saving tech, but we're at (for most users) close to all day battery life, so we're at that peak.
Then there are things like Camera tech, again unless you're a professional photographer we already have great quality photos. Why do I need more megapixels? Why do 99% of users?
You will notice jumps in speed and features as IOS is developed and if you skip a few iPhone models, but things seem to have stopped being big yearly ups around the point of Iphone 6.
We've had the same form-factor for years, piece of glass, minimal buttons. It would be fascinating to see real innovation from apple to produce something different. If apple can release a beautiful, creaseless folding phone that'd be one Idea (but hardly revolutionary).