In my opinion, every android device should have the option to use AT LEAST AOSP. The device is yours, if no one provides updated you should have the ability to sideload an OS of your choice.

Obviously this is not simple for most people, compiling AOSP for your device is not an easy task, features get lost because of vendor specific code.

What we need is a Nexus like approach but without the planned obsolescence.

But you're right, 5 years support is very nice.

The thing is, phones get so powerful these days that i don't that there's any feature that would justify obsolence.