Bartra's development over the years since he got to the first team for us has been shambolic to say the least.
He spent to long sitting on the bench and out of the squad here with little playing time as possible since he was promoted under Tito. He should've left on loan or completely to find a team that would give him the minutes to develop properly a lot sooner than this year.
He's 25 now and you can see the effects of years of stagnation due to little playing time. Just compare him to Umtiti and it's a night and day difference despite Umtiti only being 2 years younger than him. it's a shame in regards to Bartra, he's a nice guy but it's clear his development wasn't very good and perhaps we overestimated his skill/talent level since at this moment he's just not cut out to be a top level CB.
It isn't just playing time tbh,as someone mentioned he didn't earn trust of any Barca 1st team manager. Neither Pep (he was 21 when Pep left),Tito,Tata and Lucho ,his own former coach that brought him to recognition with B team trusted him.
He isn't strong,athletic,tall or quick. I mean many gr8 CBs was shorter or slower but few lacked all the physical aspects like that(by lack I mean lack being gr8 in one of those aspects),and those few had been really smart and talented while Marc isn't that talented or smart.Umtiti for example is shorter but faster,stronger and more athletic. Pique is taller,stronger etc.
He simply was never cut for gr8 things,neither his talent or physical tools would have helped him to reach the level needed to be starter here. Good overall player but being good is just not enough.
Wish him the best,he was a loyal nice bench player for us. But we aren't the blame for his level.