I don't expect iOS 11 to run well on it. You're making up a strawman and attacking it, acting like you're making a point.
What I do expect is to be able to keep running the version of iOS that does run well on it. I want to run iOS 9 on my iPhone 6, because Apple has decided that it's better for me to have a phone that runs at a snail's pace and there's absolutely nothing that I can do about it. BTW, iOS 10 was released in 2016, 11 in 2017.
Having said that, there's no reason that basic functions like typing letters becomes slow and laggy. The 6 is still like 10 times more powerful than a 4S, 20 times a 3GS, etc... yet those devices could enter letters without delay. How bogged down has iOS become that playing a song or typing a message is a slower experience than it was years ago. Even people with iPhone 7 and 6S are having slowdowns with iOS 11 (though in many cases it could be from that pesky CPU throttling they secretly introduced).
How high a horse you must have to laugh at people who either can't or would rather not replace a phone with a nearly identical one every 2-3 years just because a permanent and often forced update turned their perfectly good device into a relic.
