I always used to think "build from the back" when assembling a squad, make yourselves tough to beat & then go from there. Probably stems from the old George Graham at Arsenal days & more recently Mourinho where they would happily bore their way to 1-0 wins to achieve the end goal.
Reading a lot of coaches blogs, tweets etc. over the summer though, the newer consensus seems to be get the attack right as that really defines the way you play, build up, create chances etc. & that it's much easier to correct a defence in a shorter period of time.
If you look at what Klopp did with Liverpool he prioritised attack initially & it made them competitive then when he added VVD, Alisson etc. it took them to the next level.
Now, I'm not in any way saying that's necessarily what we're doing but we struggled for a clear style of play last season that we were comfortable with & could impose on most teams. With Waghorn mentioning in his interview about being told about us wanting to press high & defend from the front which we weren't consistently good with last season I think there could be some credence to it.
The addition of Maatsen to compliment Dabo would certainly indicate trying to play in the opposition half far more.
The back 3 are still a concern, 100% but they at least know what is expected of them, the way they get on the ball & play is 2nd nature to them by now, upgrading their quality & balance with the likes of Clarke-Salter should be a fairly easy transition in my opinion.