Oh dear. You sound like you have no idea. We have to use text books when we teach students, it gives them a reference point and a chance to prepare for and review classes. Of course we shouldn't rely on them wholly, yet we should rely on them as THE guide for our classes by covering the grammar and vocabualry specified in each unit. The importance being that it gives the students some structure, so they are not overwhelmed with too many grammar rules or vocabulary in a single class.