To explain again, Sasuke has 3 Tomoe in his eyes, while Shippudeen can use Genjutsu. The same way he can use it in the Classic Series, he had 3 Tomoe as a child.
As for facing Sukuna, Sukuna has too much ego and it would be a fight to the death, Sukuna is a smart guy so he wouldn't suddenly risk his Cursed energy and use his D.E. instantly because he is unaware of his opponent's abilities. Because he doesn't know if he has a D.E. superior to his own. Therefore, unless he activates his opponent's D.E., he will not use it himself. We saw this in his battle with Gojo. But Sasuke is someone who always takes things for granted. For example, in his first encounter with Naruto, even though he ate all his energy, he would use Kirin just to be on the safe side.