There are loads of mods that make fishing just get easier without reason, downright cheat mods. I would rather like to see a mod that makes the fish slow down the longer you have them on the line. A sort of "fish exhaustion" so that the longer you fight it without the fish getting off the line, the higher chance you have of catching it. Sound possible? PS: And yes, I am currently level 10 fishing with a cork bobber and struggling to reel in legendary fish.
I find the trap bobber better to catch legendary fish. Get the trap bobber and eat a "Dish o' the sea" and the legendary fish aren't that hard.