Yea my thoughts exactly. It's clear that his mana pool is so stupendously large that he can fire off in rapid succession, spells that others would have trouble with just to cast one of them. Which results in him never having learned anything outside of "if spell not work, use more power!"
He's not stupid as he does think things through to a decent extend, but someone should make him realise that using magic is about more than just raw output.
You get it! He's not learning things out of his expertise （/TДT)/ I kinda wanna see him with some unconventional magics a.k.a. unique spells
Or at least unconventional ways to use spells. Not just "damage spell x100, barrier x100, dispell x100"
LMAOOO RIGHT
I thinks it's because of the lack of knowledge he has on the world. Considering he learned it all from books and he's too overpowered, he's not even bothering to try practicing spells and dispels it as he likes. Yuuji is kind of similar to Saitama, one hit and it's done. So now that he faces dilemma, he continues to pour out mana
It seems like he's relying too much on output... Not utilization. In short, he is relying on things that have made his path easy and eliminate the threat conventionally. Well, at least we can see his absolute prowess.