People have been going on and on about the death of 'Tiki Taka' here and elsewhere.
How is spending hours in training drilling into teams how to keep the ball and use it with creativity and intelligence suddenly a bad idea? 'Tiki Taka' is at it's strongest when a team scores a goal or two, but is at it's weakest when the team concedes and/or the opponent line up denying space in the final third.
That problem isn't exclusive to Tiki Taka as every team finds breaking down opponents lined up around the box difficult, but it is the most common strategy to provoke that kind of tactical response.
What Pep need to find is what every team needs to find; a creative, collective solution to beating disciplined and superb defending that utilizes a large number of players to deny the opponent space.
They lost 5-0 on aggregate, I think a lot more went wrong than coming up against a disciplined team.
Possession is fine, but there's no reason you can't do that and have your keeper stay on his line and your entire defence not be in the opponents half.