The difference in quality of the images taken with my iPhone 6s and my son's iPhone 12 is readily apparently.
Likely mostly down to better software and a bit larger sensor.
I can see the difference between my 13 Pro and 14 Pro 48MP mode too. But it comes at the cost of a larger camera.
If they were to do the same trick with the longest lens camera on the phone they would either have to go with the IQ impairing bent optical path or have a comically long lens protruding
In short, the sensor isn’t better “per pixel”.
The 48MP mode on the 14 Pro doesn’t even begin to touch a 24MP camera with a 24mm lens either.
. E.g. because of the methods I developed I was able in 2007 to forcast the time span of the film revival exactly. At a time in which (almost) all others were convinced film is dead.
The real answer is that Kodak committed suicide by continuing to seek business in imaging. Digital technology destroyed value, or to put it more accurately, it shifted all value to the consumer. Today's imaging market, all of it, is not big enough to support even a single company of Kodak's size at its peak. If you combine profits of consumer imaging divisions of all remaining digital camera makers, they will be minicule compared to EK's profits in the early 90s adjusted for inflation. The most successful part of EK today is Eastman Chemical, which left the imaging business and doing $10Bn in annual sales IIRC.