Nonsense. The issue is far more complex than this.There are generally 3 groups of students in a class, interested, semi-interested, not interested. I understand the 3rd group is in the class because it makes college/university look good by raising size of enrollment.
I've yet to have a textbook that I'd consider bad. Indeed there have been a few books that I wish had more pages. I'd be highly skeptical of any textbook I purchased that was only 100-200 pages in length.Also, we must blame the textbooks. They fill the books with hundreds to thousands pages which could be reduced to 100 to 200 pages. In so doing they completely side track from the main topic any chances they get. Sometimes it seems even the author doesn't know the true meaning of a particular equation