Beef is that he's not Koulibaly.
But Gabriel is a good CB. Campos doesn't miss.
He needs to improve obviously, but there's some clubs whose defenders you simply cannot judge from how they play there. Arsenal, Dortmund, some other clubs simply have no defensive organization/tendency to concede and fall apart no matter who is on the pitch.
He was fantastic in France, had a terrific first season with Arsenal, slightly worse the second one. Wouldn't be my first, second or third choice but if we can get him for 40m or less you cannot find a better CB for less money honestly.