So is everyone else's. And so was the midfield of pretty much every team that's won the Champions League since.
Coutinho cost 125 million, Dembele 140 or whatever it was, Malcom 30 more... if they are not performing it's because they're not getting the best out of them. They clearly have quality. Origi and Shaqiri played for Liverpool tonight, Henderson, Fabinho, Milner was the midfield... you shouldn't need Busquets, Xavi, Iniesta, Neymar and prime Suarez on top of Messi to win a Champions League title.
Madrid had Isco, Asensio, Vasquez, Bale, Benzema, Morata and Ronaldo as attacking options and won it 3 times in a row with an incredibly effective offensive gameplan. Would you really trade Bale for Coutinho, Benzema for Suarez, Asensio for Dembele or Vasquez for Malcom? Personnel is the last of Barcelona's problems.
Even so, I might disagree with how they play tactically but it had nothing to do with what happened tonight. Tonight they needed a pair of balls more than they needed a good tactical plan. They should have won it all regardless of the tactics.
It doesn't stem from a single person in particular. They just don't have any of those players that give them heart and all great teams must have one of those.
One time it can happen, but how many times have they completely shat their pants away from home in Europe in the past few years? 3-0 in Turin, 3-0 in Rome, 4-0 in Paris, 4-0 tonight... it's insane. Even last year vs an average Chelsea team the same could have easily happened.