Your Question: Is it common that the things we learn in RT school are not what we deal with once we start working?
My humble answer: There's always going to be things we cover in RT school that we don't use in the real world. Yet I think this is a good thing. It's good because it helps you with critical thinking. It's better to know the why and the how rather just that it is. This additional wisdom is what separates the neb jockeys from the professional respiratory therapist.