As you can see Naruto has not healed gai and he just imagined an eye for kakashi.
There are limits to his technique and naruto has no medical knowledge just because he has this technique. Sakura > him hin medical ninjutsu because he's not using medical ninjutsu.
She's been useful in every situation that needed her medical expertise. Gai could not be saved by a medical ninja(naruto resotred his lifeforce) and they cannot regrow another persons eye (kakashi).
There are limits to his technique and naruto has no medical knowledge just because he has this technique. Sakura > him hin medical ninjutsu because he's not using medical ninjutsu.
She's been useful in every situation that needed her medical expertise. Gai could not be saved by a medical ninja(naruto resotred his lifeforce) and they cannot regrow another persons eye (kakashi).