Seems like maybe a bigger cause of e-waste might be the mindset that a device immediately needs to go in a dumpster the day after some OS upgrade comes out that won't run on it.
Apple also isn’t dropping support for older operating systems the second a new one hits the CDNs.
A Mac on the latest OS that it can run can still expect at least two to three years of additional security updates, so if yesterday was the end of the line for your Mac and you want to use it for a couple of more years, feel free. You won’t get Stage Manager, but from the reviews I’ve read, you’re not missing much.
2016 Macs are not "unmaintained" yet. They should receive security updates for at least two more years, which will make them eight years old at that point.
I don't recommend my friends or family put important information or sign in to any device that is running unmaintained OS software
Because I assume they're exploitable from a security point of view after that point
Of course no one follows that advice but what are we supposed to do?