Ongoing support has to be seem in the context of the market. Every phone manufacturer bases support on both original sale date and ongoing sale date. So you can’t just ignore original sale date when considering longevity.
Another way to put it is that no one does better than Apple at keeping their devices useful and valuable (easily demonstrated in resale values). Maybe Apple could do even better, but it's in a market where it is far and away the standout.
As an aside, people say "well look I can put some completely unsupported, random ROM on my old device!" is not a counterpoint. iPhones and iPads continue on as our kid's devices, resolve for a handsome resale price, etc. Competitor devices collect dust in a drawer. This is empirical truth.