I'll try explaining this to you in a way you might understand, since you're a Messi fanboy, I'm sure you've argued in his favour for psg. In the two seasons before he joined psg reached the final, and semi final of the champions league then Messi joins and they get knocked out in the last 16, maybe bayern knock them out in the last 16 again, does that mean he's made them worse? No, because correlation doesn't equal causation. For all your praise of how great we were before Ronaldo joined we couldn't even beat villareal in the europa league
final, yet as soon as Ronaldo joins we beat them home and away, so we must have been better right?
Or maybe as almost everyone who watches football knows, more than one factor matters, cavani basically started being injured unless Uruguay were playing, greenwood got arrested, none of that had anything to do with poorer performances, particularly in the second half of the season under rangnick which was worse, martial went on loan, greenwood got arrested on January was it, and cavani was constantly injured or unavailable, and the second half of our season under rangnick was much worse. But according to you the only difference was ronaldo