Unripe
Immature, Inexperienced, Not Yet Good At
noun, な adjective, の adjective
みじゅく
下手 （へた） Unskillful, Unskilled, Bad At
苦手 （にがて） Hard To Deal With, Weak Point, Poor At, Not Very Good At, Bad At
未熟 （みじゅく） Unripe, Immature, Inexperienced, Not Yet Good At
未遂 （みすい） Attempt
He's Not Yet Good At 未熟 it because his skills have not yet 未 ripened 熟