But even with Susanoo, Itachi is slow...
Susanoo take ton of chakra, he can´t use it forever.
Minato in case can teleport to dodge every move by coming from Itachi.
And I doubt Itachi is going to react to Minato speed, even Obito and Raikage failed to do.
Base Minato vs Itachi would be a high diff battle.
Bijuu Mode Minato low diffs at worst.
We don't know if he is slow with susanoo.
His susanoo byfar is the most unique one with extra abilities on top of that.
(I think eternal mangekyou solves the problem as it removes stress from body compared to mangekyou , So maybe less chakra consumption , Eternal mangkyou users don'treally struggle as much as Mangekyou users , *just my headcanon*).
Also Susanoo defense is sort of very strong , Even with Less mobility.
And itachi always had Shishui kotoamatsuki as backup. (I don't know if this counts).
(Another headcanon is shishui was proficient in body flicker ninjutsu , and itachi and Shishui were good friends as training buddies , won't be far fetched to assume he can deal with speed + Sharingan is always there. But TFRJ is on another tier only so I don't think so it would help).
And if are talking about full arsenal.
Itachi has access to Izanami and Izanagi , though a huge prize is to be paid here.
I don't think so there's any escape to these jutsu.