I think in the modern game fullbacks are one of the most important positions on the pitch - stretching play wide and getting assists like Robertson, TAA, Raum etc... or supplmenting the midfield like Cancelo at City. All the top teams have great fullbacks and they're very important to the way the team plays.
One of the things I always do when I start a new save is pick someone to build the team round and really try and get the best out of - it's usually a young winger or midfielder but decided to try it with Gaya in my Valencia save and it worked really well: