What is he possibly going to do against the strongest entity that even Naruto and Sasuke are having trouble fighting? He has no sharingan to keep up with Madara's movements, no Kamui to stop attacks by Madara, chakra is low so he can't use any of the ninjutsu he copied (since I'm sure he remembers them despite that debate going on), he can't charge at Madara like Sakura on two levels, 1 being that it's a stupid idea and won't delay Madara at all and he will only be in the way of Naruto and Sasuke, 2 he can't heal himself and would die.
So what is he going to do other than just sit around and watch? He has tactics, but again.. that's handicapped to only his normal eyes now (his tactics relied on sharingan spotting small details and such for the most part). He's never fought someone like Madara so his "sensei wisdom" is not useful. He has knowledge of genjutsu, but is that useful without sharingan to help break it easier?
The best move he can make is to take Sakura (or have her take him) out of range and let Naruto and Sasuke fight him. Both of them are useless unless Sasuke and Naruto share their abilities with Kakashi and Sakura some how and they become tanks for a short time while Naruto and Sasuke come up with something to break the Infinite Tsukuyomi? I doubt that will happen, so they are best out of the way.