Yesnth
A thought occurs his end goal should be to make a technique like G.E.R so that he can make actions meaningless or or love train to redirect Misfortune its the only counters I can think of that could deal with limitless but ik those are op so it'd be interesting if some of his abilities were stand inspired. He can make abilities that do certain parts of stand abilities and when used in tandem replicate it.
About the iverpowered thing I just wanna say even if it s logical for him to lose to gojo he shouldve been aboe to leave a mark thats the point of opness and just geniuses in general Look at gojo vs toji or idk take example from any anime even if they are less experienced than their opponents they are aboe to adapt in the moment especially shuichi with his hard to kill stuff My opinion