First of all, you’re implying it runs latest Windows - but Windows 11 shipped a few years ago.

Second - not really a fair comparison. 18 years ago the iPhone didn’t even exist. And the oldest model (17 years old) had really weak hardware. 4GB of storage, 128MB of RAM, and the CPU was an order of magnitude slower than current spec CPUs (it was also 32 bit - and 64 bit ARM is a completely new architecture - similar to the failed Itanium).

Even if it was supported, it would be a horrible experience.

What technical limitations?

I’d guess it was the small battery in the watch. A lot of features on Apple’s smartwatch cause serious battery life problems unless they can be offloaded to your phone at least most of the day.

For example if you have the weather conditions on your watch face… the watch can lookup the weather but it generally will ask your phone to do that. Stuff like that is a lot easier if you control the phone operating system and aren’t just running an app.

… for example if you never launch the weather app on your phone, both Android and iOS will reduce it’s ability to drain the phone’s battery by running in the background. Apple makes an exception to that rule for weather apps where the user has a widget an Apple Watch face. How could the Android battery management systems know what widgets are on your Apple Watch?

it’s just never used or enabled in the software by default

…and most people who own those devices have never heard of IPv6 and don’t know how to enable it. They just won’t be able to access your website. If Amazon dropped support for IPv4, there wouldn’t be anything i’d be able to do to deal with the fall out. I’m not going to send a technician to every single home of every customer I have. What I could (and would) do is move all my stuff off Amazon.