The problem is the moon looks small from here, but no one would ever have enough chakra to snipe the moon with Kamui, even if it looks small from here. Try to snipe the earth, you will notice impossible.
I'm assuming the moon is extremely huge. At the very least I'm assuming you would need the chakra levels of someone like hagaromo, if not more since it was he and his brother who made the moon. That amount of chakra, they simply didn't have. Removing the moon would pose problems, but remember it wouldn't pose too much problems as the ninja can control the elements until everything stabalizes.
that needs too much chakra ,but if naruto had supported him with all biju’s chakra,i think he would have been able to do it
the question is why didnt kakashi warp whole black egg which was surrounding madara woth madara instead of opening small hole in it for gai(remember gai vs madara’s fight)