At the time, I was struggling to keep up with the marking demands of a new (i.e. This was the first year it was taught) course I was TA'ing. I had around a hundred students and each one was generating 10-20 pages of handwritten lab reports per week. Student writing varied from human typewriter to medical prescription from a meth-addicted doctor. I tried to grade everything fairly and provide feedback about mistakes so students could learn.
My fellow TA's complained to the department that we were well over the hours we were supposed to be spending by a factor of at least 3. We were told to do less. Just to be clear, I wasn't worried about how much I was being paid. The problem was that I had my own research and coursework to do. We simply needed more TA's in that course due to the way lab assignments were designed. The prof teaching the course was apologetic and furnished me with the above quote.
This is teaching at a research focused university in a nutshell. There is no shortage of people who want to do a good job teaching, but the system is designed to force them to spend their time on other things.
Why is an institution of higher learning so hostile to those who want to put an honest effort into teaching? Just as nobody has ever won a Nobel prize for having happy students, no research focused university ranks well if they aren't churning out a lot of papers. Teaching competes with that priority.
If we want better educational outcomes for students, we need to do a better job of aligning the incentives governing universities with that goal.