We learn by being stretched ... otherwise we won't learn and grow. That's a main finding from cognition research.
Of course, I agree with much of what you said that religion courses shouldn't be the hardest course of the bunch. They don't need to have busy work. But they also shouldn't be "attend and show up and that's good enough" classes either. The religion classes that taught me the most (I went to three different schools and experienced religion and institute classes) were the ones that were tough. But usually they were tough in having me write essays that really made me think and reflect and study the topic and ponder what it meant. I thought that kind of learning was super effective, even though they were tough classes.
I'm not a religion professor, BTW ... education professor