How is 10 years of security support for the iPhone X seen as lifetime or 5 years unreasonable? You even contradicted your own statement. The iPhone 6s launched in 2015 and received 7 years of iOS updates and even got security updates as recent as 15.7.1 which makes that 8 years. Considering the iPhone X is an even more powerful smartphone, there is no reason why it can’t.Totally unreasonable to expect lifetime support for a product.
Totally unreasonable to expect software updates on a phone or computer once it is 5 years old.
I wouldn’t expect a iPhone 5s to still be getting updates. But this is the same company that described the A7 as desktop class performance. Considering the pace of innovation has slowed down and users are keeping their phones longer, there is no reason to provide baseline security updates for phones for longer. It’s healthier for the environment, better for Apples own business since that device could be serviced with a new battery, revenue for services such as iCloud, Apple TV+.
Apple will have to anyway, because people ‘are’ keeping their devices longer.