That's nonsense for so many reasons but I'll just list a couple that will right away show why it's not a valid comparison in the least. First of all, I think it's harsh to consider the CR7 transfer a flop, but at least I can understand why.
1) PSG didn't buy a superstar like you said, they bought potential. Mbappe was only one year into his professional career at Monaco when PSG shelled out 180m for him, he was not even a world cup winner then. Here we are less than a year from his free agency and there's a team offering 180m for him, that's really far from a flop my man.
2) If Ronaldo was a flop at Juve (again, harsh) then it's because he was bought as one of the top 2 best players in the world and got knocked out by Lyon, managed to be part of a rare Juve squad that lost Serie A, and (most importantly and a big distinction between the two) Juve never got as far in the competition as they did without him, all of this with having the entire team built around getting the best out of him.
So, no, the Mbappe transfer is so far from a flop, and even less so from one on steroids, I don't think you really understand what the term means.