Ok let's be serious a minute U_U
Genjutsu
It was stated during the kage summit that Sharingan can't follow the speed of the likes of Raikage(compared to Minato) enough to actually catch the person in the genjutsu. Not only that, but Minato being a sensor, can sense the chakra coming from Itachi's eye like Obito did in order to prevent against a Sharingan attack. Furthermore, Minato can also use clone, all he has to do is to create one during the battle. Itachi can see handsigns with his Sharingan, but Sharingan can't distinguish clone with the original.
Genjutsu doesn't work on clone, so Itachi would have to make sure to be sure if the one he is facing is the clone or the original to try genjutsu. Sharingan can't follow teleportation speed, so Minato can likely use a clone during one of his teleportation during the fight and hide the original somewhere else at the same time. In this case, Itachi won't even know when Minato subtituated himself with a clone, fighting a clone with no hope of puting him in a genjutsu. He can even be fooled if the clone feint Itachi into believing he was caught by one so that he could blitz him when Itachi would try to take advantage of this to finish him(if he tries to cover the distance). But even if Minato doesn't use this strategy, but on the contrary uses a clone before Itachi's sight, as stated, Itachi couldn't identity the clone with the original, and judging by Itachi's intelligence, i think he won't try a clone before knowing who is the original and who is the fake. Not only that but even if he want to play gamble and miraculously manage to catch the original(on the contrary of the clone) in his genjutsu, the clone being capable to perform Hiraishin themselves could easily teleport to the original in an instant to disturb the chakra flow.
The clone may not even do it directly and wait until Itachi would close the distance in order to attack the original(while in genjutsu) and appear instantly to finish him(Itachi being close to the markings on the original's pocket).
But if Itachi fails and only put the clone in the genjutsu, it won't work like i've stated before. But if Minato wants, he could feint Itachi into believing it was fooled by the genjutsu only to take advantage of this if Itachi were trying to kill the clone(not knowing it's one) while closing the distance to destroy him
Susanoo
Itachi uses Susanoo and? He has no way to hit Minato and it's not as if Susanoo is a technique he can hold for long, so sooner or later, he will die. Not only that, with the swaping ability of FTG technique demonstrated in latest chapter, he can take away Susanoo to leave him open for a next attack.
Tobirama for example managed to teleport Obito during this chapter
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. The same thing can be done between a Susanoo and his user since the chakra based Susanoo
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to the user. With the use of clones then, Minato has the means to bypass the defense and all that without taking risks at all
Minato low-mid diff U_U