Thing is, new operating systems don't always slow down older hardware. Sure, at some point there may be a limitation that prevents upgradinh due to a lack of resources. In the early days of computing, a new OS added enough weight that it did slow down older systems.
But take Android. Recent versions have been generally faster, on the same hardware, than older versions. Even after Google dropped support for my old Galaxy Nexus, it ran a community ported version of Kit-Kat (4.4) and Lollipop (5.0) just dandy. Sure, it might have been a bit of a small footprint for more demanding new apps, but the new OSs ran better than ever. Or take Windows 10... that ran great on my old Intel Core 2 Duo laptop, better than Vista ever did.. nearly a ten year old device, sadly died recently of delayed head trauma (a busted screen hinge finally fatigued the screen connector).
So it's not a given that Apple's new OS destroys the old hardware. But hey, it's Apple, and their agenda is clearly built around a 2-year device life. So let's say it did run like Chris Christie on an iPhone 4s. Apple could have not supported the 4s... if it can't meet their performance standards, they should drop it. Yes, it's much worse when Apple dies that because, unlike Android or Windows, Apple doesn't care about backward compatibility.
So let's say they decided it ran well enough. Honestly, if their promotions claim that it's bigger and better, maybe users should be cautious. But they're making the claim it's the fastest iOS ever. Unless they have a big, hairy asterisk after that statement explaining that, hey guys, "fast" is just a marketing term and we don't actually expect any old supported device to run faster, well, they have decieved at least some if their customers.
