Manichaeism did run into a lot of practicality challenges. In particular, the restrictions on diets and behavior for the priestly class were very extreme. No harvesting food, no stepping in puddles, strict veganism, and celibacy.

I read a few books on it for a term paper in college, and the part that most sticks out in my distant memory is that the creation myth involves a lot of what were translated in my copy as aborted fetuses.