Yep, Aubameyang became one of the Barcelona players who can perform well last season. Sadly, Barcelona signed Lewandowski and forget his contribution last season, then Aubameyang lost his position as the main CF in Barcelona lineup. It is another sad story in Aubameyang career, but I am sure he doesn't lose his spirit to play at his best form in a new club (Cheslea). There is no problem with Aubameyang skills, he is still a sharp or productive striker. So, he should have no obstacles to perform well with Chelsea team.
I don't think Barcelona has forgotten his contribution, but something has to change and the club has to take steps forward to continuously improve the quality of its team. The positive thing about Auba is that Barcelona managed to restore its performance last season so that teams like Chelsea are still eyeing him. While he is happy with his new club, Auba still wants to compete with other strikers at Barcelona.
Chelsea must realize their weakness at defense line, that's why they sign Wesley Fofana. I assume Chelsea defense will be strong again with some new players. Their strategy will be more effective with new experienced and skilled players. Just wait for an improvement on Chelsea perfromance in the next few matches. Be calm!!
Their top 3 defenders left this season, it was Rudiger, Alonso and Christensen. So their defensive power would obviously be weak without the addition of new players. So it's natural that the team's performance is currently down where Chelsea are only able to win 2 times from their last 5 matches.