Aren't you asking the wrong question? Even if he was exactly what he was last year, he would have to change. He can't play like that again. He has to modify his game to compliment obviously better players. Even with no drop off, he was never was as good as Jaylen is now.
I'm still hopeful, but I'm also not really convinced that last year's Kemba can make those changes. Its not like he is trying to play differently and is failing at it. He's really just trying to play like he did last year, and is failing at that.
I think it is even simpler or more fundamental than that. He is just trying to get his core skills and conditioning back. Then he can worry about fine tuning his game to be more or less the initiator of things or more complementary . If he isn't able to get the core skills back to a reasonably high level, it won't matter how he adjusts his game. In fact, he might be adjusting to coming off the bench.
The answer to the poll question is yes, as of right now, coming off rehab and knee procedures, he is missing a step, his skills and ability are well below what he was mid last season. The tougher question is whether this is part of a normal rehab and recover process or if the drop off is permanent/irrecoverable. Right now, I think it is more the former than the latter but I also have plenty of concern that he is one awkward landing from a set back in terms of his knee which will result in needing rest and further delay his progress toward restoring his skills.
To me, this is far more about his knee holding up than any ability or willingness to adjust his game. I don't have any doubt that he can adjust his game and will adjust his game to help the team win. He is a smart, experienced, player who has the right attitude. If he has his game, he has plenty of ability to do what ever he needs to do with his game to fit in with this team.