pogba was crap for the majority of his 2nd spell at manure. he played close to his abilities after mourinho was fired, but he faded back to mediocrity after a couple of months.
my point is that many players, even a potential world class midfielder like pogba will eventually regress after leaving juventus. if i had to pick some players who started or continued to shine after they left in recent years, i couldn't list too many players. llorente had a nice spell at spurs, vidal and coman were good for bayern, and that's probably all. most of the others we sold usually regressed. (immobile doesn't count, he never was part of the juve squad under this management.) the work ethics aren't the same everywhere i guess.
bottom line is that kean showed plenty of talent for us, especially his finishing was exceptional. he could have had a completely different career had he stayed.