There is so much time, effort, and physical waste that is generated by slightly redesigning phones every year purely for the sake of making sales (as opposed to meaningful improvement upon the existing design or introduction of a new hardware feature). Think not only of people upgrading for the sake of it, but all of the cases, screen protectors, and other assorted accessories cast in plastic for previous models that are garbage now.
It would be nice if we could just space these things out to 5 years or so now, because that's probably how long it takes for anything to change enough to justify a new model.
Great many containers filled with stuff from rich countries find their way to poor countries, some include stolen goods (like cars), others include garbage, most include goods that still have some value for other people, including tech.
Maybe the problem should be looked at from that angle, and maybe there's no problem, really. One's garbage will always be another one's treasure.