It doesn't matter if it is unfair. People are checking out on old stuff and giving up right away because it is so slow. Everybody told them it should be fast, but it is not. It will never get close to the speed of modern machines.
Discussion
I wouldn't say that Linux will make their old machines fast, I would say it make them unable again.
I didn't say this before but conversation and setting realistic expectations is what you ideally want.