Have you not been paying attention to how they’ve succeeded? The large part of that squad have spent years at the club. They have an understanding of how they play that means even if a player makes an individual error, someone else is there to cover it straight away. It gives them more confidence to defend, press and at set pieces.
That can only come through time and makes them greater than the sum of their parts. There’s a reason Craig, Swanson and Drey Wright have looked a shadow of the players they were at Saints compared to their time at us.
You don’t develop a good team by chopping and changing all the time.