trying to reach above one's station and failing; trying to accomplish something beyond one's abilities and failing; monkey catching (a reflection of) the moon (in the water)
yojijukugo (four-character idiom)
あの計画は、まるで猿猴捉月のようで、非現実的すぎた。
That plan was far too unrealistic, like chasing the moon's reflection in the water.