If you don't understand fishing and can't be bothered to learn, you don't deserve the fishing credo. But I agree with an earlier poster, you don't deserve to be locked out of 90% of ALL credos if you can't stand fishing.
One thing I like about this game is that if your character is born into a civilized village, he doesn't have to do the hunter-gatherer thing at all. He can be a domestic cook/smith/farmer or whatever. He can do what we do in real life and stand on the accomplishments of previous hunter-gatherers and live in a civilized world. But credos throw that out the window, because they force even some scholar or soldier to get out there and pick flowers and fish.
IMO, there should be a way to 'teach' credo prerequisites to one another, similar to how you teach combat moves. So if there's a fisherman in my village who has completed the credo, I should be able to use him to unlock credos gatekept by fishing without doing the fishing credo myself. Maybe there should be a time gate to doing this (the fisherman can only teach one person a month or something?) but I feel like it would stop the forced linear progression problem with credos. And teaching this wouldn't give me the benefits of the fishing credo, it would just let me skip it as a prereq.