So you think that Apple should somehow ensure that the battery lasts longer than possible? Or would you rather the phone just be dead once the phone reaches a point where the battery can no longer supply the proper power? I guess I am just trying to think of what options they honestly had. The only one I can think of is letting people know of the issue and offering to replace the battery for a fee. I don't think they should just be replacing batteries for free.
Battery fall off is predictable. Apple knows pretty much exactly how much battery will be left after 12, 24, etc... months of use. There's no reason Apple couldn't have known that the iPhone 6 would not function properly after 2 years. That the genius at the Apple store will tell you the battery is fine and refuse to even sell an upgrade to users whose phones are getting throttled is just icing.
Lastly, if what Apple is doing now is just common sense because batteries degrade, then why wasn't it needed for the first 8 years after the iPhone was released, and why doesn't every other phone manufacturer need to do it?