Chelsea miss a Fabregas-type player the most at the moment - someone who could produce brilliant long-range shots opening up the defense. They look absolutely anemic in the middle of the pitch. Kovacic has done okay, but there's no real creativity. Jorginho is hopeless - it is amazing how long he has managed to play in a top side without doing anything defensively and almost nothing attacking-wise. Mount is just an average footballer. Kante has performed well.
I think they will do okay once they get Ziyech into the squad. He can produce brilliant crosses for Werner and Giroud to attack. And Pulisic, of course - they miss his creativity! They looked fairly settled in defense up until that Christiansen blunder. Again, Alonso is a liability; he does very little defensively, is very slow, and other than an occasional cross or a set-piece, he does absolutely nothing in attack.
My impression is that this is not a bad Chelsea squad considering five first-choice players are not fit - Ziyech, Chilwell, Mendy, Pulisic, Silva. They might just have enough to finish in the top four but won't trouble the top-two at all.