What annoys me about McCabe-Theil diagrams is that they are not fundamentally the way the theory works for designing distillation systems. They are basically a way to solve problems using huge approximations before we had the computer power to do it correctly. I much prefer the rate models for distillation column design and think that mccabe-theil should be scrapped. HOWEVER, I think that students need to understand how that stuff truly works and since the algorithms are simple they should write a basic rate equation based solver for distillation column design. Then they would truly understand how the stuff really works and be better equipped to use it.
I just don't like the idea that you learn one method that is supposed to give you the idea of how things really work but then the actual systems you used are based on entirely different theories and assumptions.