Many teachers don’t want to skip the basics when their teaching a class because that’s the time to bring everyone up to speed so that you’re all on the same page before you advance to more complicated topics. Or what you consider to be “bs,” others may consider to actually be an integral part of the subject they are teaching, and skipping it would do a disservice to their students. What is “old” to you may not be old to every other student in that class, just like what is new to you may not be new to them. In other cases, teachers do start with what you would consider the “new stuff” and still need to take time during the class before the exam to teach new material. Some teachers might hold off on teaching really challenging material on the first day to give some buffer room for students who add the class late or are on the wait list or switch classes or haven’t been able to get the textbook yet. It’s not as easy as just “moving all the material up one day.” At some point, you run out of days.
Also, if this is such a concern for you, why don’t you just work ahead? The syllabus typically lists what topics will be covered on which days, and if you know what will be covered in the class before the exam, then you can work ahead. Read the chapter, work through some problems, consult resources or videos online. Then during class, you’ll be better equipped to understand what the teacher is explaining and you’ll be able to ask any questions during class. You can also go to your professor’s office hours before the exam and ask questions you have about the new material. If your professor doesn’t have office hours, then you can make an appointment to meet or email them questions. You can form a study group where you all explain the new material to each other before the exam.
My point is that the world is not always going to work the way you want it to. You are (or are on the verge of) becoming an adult, and you need to learn to adapt to situations. There will be millions of things that you will think are unfair or that you will think could “easily” be improved. But you can’t bend the world to be what you want it to be. You know the situation beforehand (especially since this is your third midterm) and you can plan accordingly.