Even the likes of Ruud Gullit have recently highlighted his individual performance needs improving too. I like De Jong and think he has great qualities but currently he's not being used effectively.
To be honest, I personally don't think the midfield looks any worse off when he's not in it currently and his better performances have been at libero, where he's able to progress the ball into space up the field and can then lay it off.
I definitely wouldn't sell him but I think he would benefit massively from a coach that can help him understand certain aspects of midfield play, where he should be occupying positions etc.