For current phones I think 5 years is a good support window, the batteries don't last much longer than that. But if replaceable batteries make a comeback (and I hope they do with the push from the EU), then I definitely agree that more like 10 years should be demanded as reasonable.

Especially for something like Android where if you compare a flagship from 5-7 years ago with a brand new Android Go phone the level of performance & feature set is not really that different. So it's not like the OS gets to actually start expecting things like a high end Vulkan capable GPU & neural net accelerators or anything. It still has to work with what is essentially old hardware anyway just in a brand new body.