Where does he even remotely imply that because some don't have issues, there is no problem? He says that a slow update doesn't make the device unusable. It obviously doesn't run as well as at did, but still being able to use it means it still works. He goes on to mention that some people won't even notice it, which is very true.
Of course, "not quite unusable" is pretty bad for an Apple device. Despite what some people seem to think, Apple doesn't want to make any iOS devices slow- doing so makes people not want to buy iOS devices in the future. But so does not providing updates, and so does letting people choose to downgrade to older versions and complain about new features not working on their device.
