I felt that way when studying math in college, but after sometime I actually came to like the use of "clearly" and the like as it can be used as a check on whether you've spent enough time internalizing the previous information. It's one thing to have a text or a person hold your hand through algorithms or theorems, it's another to be able to do it yourself. So getting hit with a "clearly" that feels unjustified is often a signal to let go of the guiding hand and go back and review until the statement in question does become clear.