"Building something" is the director of football's job. Pep's is to win trophies. If he wins a bunch then leaves it's job done.And conceding goals at important moments, which he can't do anything about.
One of my misgivings about signing Messi, is Pep doing a Pellegrini & forgetting about building anything, just cashing in on trophies & then fucking off, with Messi.
There is no reason we can't put the same effort into fixing the defensive play, as well as the attacking play.
We see with Barca now, what you end up with if you neglect the other parts of the team.