it's actually not a bad move for Kubo to make the most powerful person in the series incapable of using said power to it's fullest potential. If this kid (and Inoue) were intellectually sophisticated, they'd be TOO powerful and there'd be no one to stop them.
characters must have a weakness, fellas.
Also, his reality warping isn't weaksauce. 😐 not sure how you came to that conclusion. he literally just created life... that's far beyond anything that has been done in the series thus far.