I guess it depends on which players you pin down our recent CL meltdowns. For me:
Vs Liverpool: Rakitic, Alba and Coutinho - all complete zeros.
Vs Roma: Busquets, Rakitic and Umtiti.
Maybe a better fullback could have made a difference, but then again who? Carvajal, Kimmich and Arnold have been better. Thats it. Every other fullback (like Semedo) is at best a slight upgrade. Or worse.
@DonAndres: The difference to Rakitic is that there are/were better midfielders available. We cant just raid Madrid or Bayern. Or get Arnold. My point: do the classic routine: keep one of the solid guys (Roberto or Semedo), get a decent talent as backup and hope for more.
Part of it is the combination of horrible scouting and coaching. To Barca, a talent doesn't exist until they're already outrageously expensive, or "la liga experience". Look at what Bayern did with incredible scouting on Davies, or RM discovering a talent like Hakimi early.
We had Mateu Morey who was an extremely promising La Masia talent was let go a year ago, even though he did want money I think the club has to be smart and give in to some demands for prospects that have the ability to make a real contribution. His potential is seriously high and he could've made the RB role his own, he was a standout player in multiple international tournaments and for youth club teams. Just debuted for Dortmund recently and had his first assist yesterday.
On the other side, horrible coaching prevents us from being able to galvanize the average talents we have to play like something greater. Chelsea were able to win a PL with the likes of Alonso/Azpilicueta looking great who many consider average talents. Who even knows how someone like Robertson would do without Klopp there, although Trent is a wizard.
I've little doubt someone like Klopp would have done way more to get the best from Semedo than Valverde did, as Semedo really did look like a great talent at Benfica. In fact, I would say Semedo has looked absolutely great under Setien and should be given more of a chance before getting disposed. He has been a constant attacking threat in those games and had more attacking moments in a few games under Setien than entire seasons under Valverde. Including a key assist in an away CL game vs Napoli.
Firpo too isn't necessarily a lost cause if we develop him right.
Right now I would look to buy back Morey if possible or to get someone like Sergi?o Dest. Players who are really talented offensively early on can improve their defensive IQ over years, more easily than the reverse. And look to other teams relying on young players (Trent, Kimmich few years back, Davies) to see that being U23 doesn't automatically mean they should be 2nd option behind Roberto just because he's Catalan golden boy.