In the Helena Curtain scenario, which is happening all over the country right now today in classrooms near you, the teacher doesn’t have to embrace the extremely radical and hugely effective idea that comprehensible input really does mean creating a din of uninterrupted L2 in the minds of the students.
Comprehensible input and the textbook are like oil and water, because in the one the focus of the student is fully on the meaning of the language (which allows the deeper mind to actually acquire the language in a magnificent unconscious process) and in the other the focus of the student is on the language itself.
Focusing on the language itself is a conscious mechanical process, and leads to few gains by only those few students who are capable of the mental gymnastics required for such foolish work, and even those gains in terms of elegance of expression suck anyway.