I don't think its too bad a situation tbh. 4 fullbacks, yes 3 are young but 1 has played nearly 150 top level games. Whether or not you rate these players is another matter, but the club has 2 fullbacks and then two pushing them so long as they're fit.
Unless you're Man City you don't have 4 of close quality and experience, even Chelsea throw in Bertrand when Cole is out and he's a very ordinary footballer.