We loaned out Angelino in something like 2018 to the likes of Girona and Mallorca eventually selling him to PSV, We bought him back and he was nowhere near good enough (Realistically we bought him because he had a good year at PSV and we had an cheap option to buy back and we knew we could make profit on him by selling him again).
I really don't know how you are coming up with "6 years of failure" how on earth have you come to that conclusion?
● 5 trophies in a single season
● Treble
● 4 Premier League Titles in a row
Angelino was actually more of a Left Wing Back, He wasn't a left back, He was shocking defensively.
Plus Pep wanted to go down the route of playing a left footed centre back at left back which has worked a treat, Ake has arguably been one of the best defenders in Europe of the last two years.
Now we have Gvardiol at left back who was absolutely sensational in the second half of last season.
Obviously we all have different views, I just find this one really strange that you call it "6 years of failure".