Gonzalo has delivered what we needed: goals. If you look at his stats at Juve, he is far from bad, altough not as good as his Napoli days. :
44 goals in 83 appearances for us is pretty acceptable numbers for a striker.
90 mill was maybe a bitt stiff, but he did a decent job.
Then you have to consider our way of football: When Higuain played with Napoli they were one of the highest scoring teams in Europe. They had a thing for trashing small teams, often with a big scoreline. Pipa had his share of easy goals in those fixtures. Then you have Juve, who often control those type of games, score a couple and then rest ourselves for bigger tasks.
The problem now is that he is declining and we need to look for a replacement sooner rather than later. He will never be the same player as he was in Napoli and we should start to acknowledge this.
His pace, physical condition and overall athleticism has naturally declined. Now he is more of a target man than anything else. The days where he can take on 2 defenders on his own and outmanoeuvre them is over.
We should dictate him to work around the box, not spend all his energy chasing down opponents in pressing. This is what i also see him do a lot: work in areas of the pitch where he is not a threat. i dont get it.
Focus his work on doing basic things and what he does best: receive the ball in the box and finish. I know it might sound very underwhelming, but i believe he can be a much more effective weapon if Max stops expecting him to drop down and start our build-ups all the time.
He is still a usefull player, but limited. I hope he improves after the break. best of luck.