Liverpool haven't had a disappointing season. A disappointing end.
United have had one of the worst in a couple of generations.
Not even comparable.
Id argue the average Liverpool fan will be far more heartbroken about this season after it ends and 5 years from now, than the average United fan who will just look at it as a transitional period, a forgetful year of lulz at worst.
They will remember it, in a negative way because of the ending. United fans will just brush it off, think they already have, its not a big deal.