While upgradeable is one aspect - another big aspect of the problem is it being fixeable. Due to a variety of reasons, it's not affordable to fix your old phone

While upgradeable is one aspect - another big aspect of the problem is it being fixeable. Due to a variety of reasons, it's not affordable to fix your old phone, you might as well buy a new one. FairPhone is another phone project, which aims to actually make your phone repairable too. I think it'll make a bigger dent in the short to medium term.