Electronic devices usually get thrown away because nobody wants them anymore because they are obsolete. Having removable RAM will do you little good if you can only fit ddr3.
Easily replaceable batteries would certainly extend the useful life of many devices, though.
That's why you'd want to be able to replace the mainboard, screen, keyboard, speakers, trackpad, etc., and not just the RAM. Like https://shop.mntre.com/products/mnt-reform, but presumably easier for non-technical people to use.