He is definitely not the player he once was. As a player gets old, the consistency becomes the problem and that's why BO5 becomes harder to win. I think it won't be easy for Djokovic to win a slam at this stage, but nothing is impossible. I guess he needs a lot of luck to win a slam now, but it is still a possibility, just not as high as it used to be. If Alcaraz and Sinner are both out, Djokovic can still win a slam, although nowadays there are more than just two players who can beat him.