United have struggled to live up to expectations of fans and pundits in the second season under the Dutch tactician, as they find themselves down in sixth place on the Premier League table.
The Red Devils have also failed to progress to the final stages of all domestic and continental cup competitions, after being eliminated from the UEFA Europa League by Liverpool in midweek.
Kluivert, a former player under van Gaal in his early years at Ajax Amsterdam, provided a deeper insight into the 64-year-old manager after a short spell as his assistant coach with the Dutch national team.
"With young players he is amazing, he's fantastic. Sure, also with experienced players but some players who are experienced have their own vision of playing in the game. That does not always go well.
"He knows what he wants. He is very honest, he is very straight and that's a characteristic that suits him very well."
Meanwhile, the former Barcelona striker concedes current Dutch international Memphis Depay is in a difficult situation but is confident he will come good in due time.
"[Depay] is in a little bit of a difficult situation," Kluivert added.
"But I hope for him, because I know Memphis very well, that he will succeed. If he can focus on the game he will succeed.
"A young player needs time in a new club with new players around him. At PSV he was the star and now he's playing among other big, young stars.
"I hope he will succeed because he is a good person."