Mbappe had his penalty saved as Real lost 2-1 at Athletic Bilbao.
Guti said on DAZN: "I applaud Mbappé's decision to take it.
"Mbappé has always taken them. Here, in France or at PSG, and even if the player failed in Liverpool, if there is another one you have to take it, although it is true that he is a bad shooter."
Guti then analysed Mbappé's effort at San Mamés: "He opens his foot a lot and makes it clear where he is going to shoot.
"It was a bit of a throw-in like the one in the Liverpool match. At mid-height, where you give the goalkeeper a lot of advantage to be able to stop it.
"Mbappé is not well positioned, and then, the truth is that he makes it very clear. I think he opens his foot too much, making it very clear where Kylian is going to shoot."