We don't have a pivot midfielder that comfortable sitting in front of the back. Either Rodri ball winner, nor deep play maker like Jorginho.
VdB even as a 6 or 8 likes to push forward. He's more suitable for midfield 3 which we can't really do without a pivot player and having to accommodate Bruno. It's not suitable for a double pivot as McFred despite these 2 having problem of their own.
In another word, despite comfortable moving around in different role, VdB is a system dependent player, and we yet to build a system to utilize him.