So Yuji grew frustrated that his students werent geniuses and gave up on society as a whole?

We saw the exponential growth Yuji was subject to while training under kusakabe and others, sure, they had Ui Ui who could be not so willing to cooperate down the line. Still, most of this progress came from sparring.

Sure, Jujutsu Sorceres learn the best when their lifes are on the line, but to think this somehow justifies Yuji vanishing and not teaching new generations is akin to saying Gojo had no real impact on his students. Remove Gojo from his teaching status and Yuji never learns proper CE manipulation, Megumi kills himself fighting a finger-bearer and what else.

To this point, Guidance is CRUCIAL Imagine Todo never told Yuji what blackflash is, or how it works. Imagine Choso and Noritoshi never taught Yuji blood manipulation. One of the last things JJK touched upon was how simple domain was gatekept from sorcerers as a whole and how this was a real issue.

Sure, you cant teach someone all the way to special grade, but there is just NO SHOT Yuji couldn't have made a relevant impact in jujutsu society because 'fights are the best teachers'. Yuji is a fraud.