As far as featured vassals in the manga up until now go, Shun Sui Ju is undeniably among the best seen so far. He is highly intelligent, competent and resourceful, and he has an actually interesting background with his affiliation with the tribes to the north of Zhao.
Being a stoic with a shitty haircut and hero worship complex doesn't negate all that.
It certainly doesn't make him cringe, but that word has lost all meaning. People just can't say they don't like a thing or didn't care for it, just expressing it's not for them isn't enough. It has to be wrong. Something has to be at fault.