"그들은 기본적으로 같아요."
Translation:They are basically the same.
I think it needs to be conjugated into 기본¦적(인) parallel to base+ic=basic. The (인) even lines up with the way -al isn't always used to make a word on the N|ic structure since it doesn't inherently add a difference in meaning, it just follows a sometimes convention for creating commonly accepted word forms. e.g. egotist|ic|al