I think the problem is definately in our midfield, in the setup of 4-4-2 diamond.
Busi - Is playing too far from him (he is a DM), can't pass to him, unless he pulls off an amazing aerial pass.
Rakitić - Plays it too safe, sideways passing, ball hogging.
Denis - Gets fouled constantly and losing the ball.
Iniesta - 33 years old, can't run like he used to, still the best link to Messi in attack.
Paulinho - He should be the link in the chain between midfield and Messi, but he sadly doesn't do it, he spends the most time in the box waiting for crosses.
Gomes - Is Andre Gomes. What do you expect from him?
Wingers - Non existent, only Alba, who is essentialy playing like a LWB, offers some support. Semedo/Roberto don't do it.
So all of that results with Messi dropping into the center circle and trying to dribble through the middle.