I think it can be achieved with some motivation and confidence instilled in players. But i don't see lucho doing that but he should try at least. CL might be the most toughest competition but it is also the best trophy to target. Dortmund reached final of CL by neglecting league. Real also slightly gave up on liga for their la decima. Even Chelsea tried to do the same thing but Atletico wanted the trophy more. Not saying we should give up on liga completely but we should concentrate on cl more if we can't gain the consistency needed to win the league.
It is not like we have have worst squad in europe too. We are still in top 5 or 6 imo, so with some luck and proper defensive tactics we might reach the final. Argentina in the world cup was a good example. They had a stellar attack but still they played defensively and reached the final, same case with barca right now. The problem is we have too much pride to play like that, i think that is a big problem. We are not winning matches/trophies or playing good football. We should at least have the pleasure of one of those things.
About not having good defenders to establish that style i don't think that is true exactly. Many average defenders look like goats in a conservative style when they have good defensive mid like masch. Mathieu Bartra and Pique as the 3 center backs would be good. We don't need to play like every match but we should at least try it in some matches and see how it goes. One or two matches is not enough.