I see where you are coming from. I happen to think Delph could have been very good, but was probably never fully fit. Barry is probably a good comparison too, buit getting Barry at age 25 rather than 31 or whatever we got him at. You have to be very good to get in a side that has been 95+ points 4 out of the last 5 seasons or whatever it is, even as a fringe player.
As for Doucoure, I still think he can be a key man, but unlocking how to get the best from him is important. You can structure a team that the 6 you just want a destroyer, similar to what Doucoure did v Palace, but it seems quite obvious Lampard wants someone who can distribute the ball. You sort of see that from him trying Van Der Beek in there. With Doucoure, you have to find a way to let him off the leash. In fairness to Benitez, he kind of utilised Doucoure brilliantly at the start of the season, and his injury was probably the key moment where it all fell apart.