Considering all the feats we've seen from Naruto and sasuke. The way the writers displayed them vs jigen in this battle was not only disrespectful but blind and not considerate to their true potentials.
Continually. Jigen/Isshiki is the Orochimaru of the boruto series. Isshiki is/was urashiki's partner (I so believe it). I think the destroyed tablet when sasuke scouted out the dimension jigen was in and saw the pillars and what not. The destroyed one was isshiki's. He probably disbanded from urashiki and went and did some funny shit to jigen (a whole lot of other things could or would have happened but this I think is one of them, pertaining to isshiki)