They still need plenty of time to stabilize.
You're right, with the rest of the squad and minimal funding, I think xavi is a great coaching candidate of the future. Xavi has made Barcelona better, if you look at the beginning of the record to date of course you will say the same as me. With a little spending funds Xavi tried to maximize that. Buying Aubameyang is not a bad thing, Xavi certainly already has a plan with him. Maybe if they had a lot of funds they would buy a lot of star players.
Xavi has shown how to manage a team with many limitations. Whereas funds are one of the main supporters to support the team to become a winner. Buying Aubameyang is probably the most optimal thing to do than buying a striker who is even more superior but has to go into debt to pay his wages. So I'm sure Xavi will achieve his best during this competition.
From what I have seen in a very small amount of time, Xavi is tactically quite good and has a way to connect with his players. Since Auba is not from a tiki-taka background, he might need some time to get used to it.
So, Xavi will have to play an important role in making him comfortable and using Auba in the best way possible.