Has a profession, doesn't use it. Has a fishing skill, doesn't level it. Has a luck stat, doesn't increase it. Has mana and attack power stats, doesn't need them. There isn't even the interesting caveat of beating stuff up with a fishing pole.. nope, he uses a sword.
This is just a generic wish fulfillment novel that doesn't engage with the initial premise at all beyond using it once to gain power and proceed to do whatever he wants. You could replace fishing with a gatcha, check-in, or treasure chest and it would make no difference to the story.