Real Madrid made a mistake by hiring Mbappe and spending too much money for a player like him. Real Madrid had a much better option but Real Madrid couldn't even use the penalty kick they had.
However, we can't blame Mbappe for everything and he is just a part of this team regardless of his getting the lowest rating in the game against Liverpool I'm sure he was trying to do his best but it was not enough since Real Madrid still lost the match with a 2-0 result against Liverpool.

It was of course not a mistake to sign Mbappe and since the cost for signing players like him have gone through the roof in the last decade, it is not as if Real Madrid gets to choose what they pay for someone like him. He is essentially dictating what clubs have to pay him. Besides the performance on the field, players like Mbappe bring value to the club in other ways, too. His jersey sales were said to be 450% higher than those of Bellingham and this keeps going.
But at the end of the day what counts is what he does on the field and while I fully agree that it has been strongly disappointing so far, I don't know how long he will take until he finally gets back to old strength, but I am pretty sure he will and then you would never argue again that it is wrong to sign a player like him.
For now it remains to be true what you have said, but the basic idea that he was too expensive and not worth the money seems to be off to me. However, the photo you attacked about him tells quite a bit about how he plays and behaves and this body language is one of the problems I have observed for a while now.