On top of your point, I think people should also understand that smartphones aren't exactly a small purchase for a non-trivial population. Even tech-literate are stuck with the stock ROM if they need to use banking apps, snapchat etc. because of SafetyNet.
Despite getting a lot of crap online, it looks like iPhones actually do better when it comes to shipping security updates to old phones? [1]
I am not sure but if that is really the case, I think I'll switch to one for my next phone.