That's the problem Kishimoto never addressed. Among many other things. Madara only used Susanoo when it comes to MS abilities. So where are 2 other techniques?Itachi clearly stated susanoo can only be awaken after waking 2 abilities first. Madara said that Amaterasu jutsu is trash. Meaning he probably have it and find it useless since it can ruin all the fun he want on the battlefield. Obito only had one MS the whole time and plot-no-jutsu don't want to make him seem too powerful.
Sasuke mastered Amaterasu far better than Itachi. Leave him alone and fall back. At the end of the day, his control over Amaterasu and susanoo is not easy at all. Chakra manipulation ain't easy and sasuke took it to a whole another level on his own. Even orochimaru was surprise. All that training Naruto been doing in part 2 was just catch up since Jman refused to give him some serious training over the time-skip.
No one denied that. No one attacks Sasuke, we're just discussing his powers and their origin. If you feel offended, you leave him and fall back.