OK that he was present in one of the most imporantes moments in the Club's history, but that doesn't change the fact that today he is a poor choice, the team urgently needs a defender, and they're signing a defender who doesn't have any quality to the position.
If you follow football knows very well how much he's been mediocre, when it comes to the point of opponents celebrate a signing of the opponent understands very well the level of the player.
The last match it summarizes well what I'm talking about:
David Luiz's last PSG appearance (in 3-1 loss at Monaco): conceded penalty, taken off on 62 minutes, 2/10 from L'equipe.