I think that fishing is incredibly boring currently, an I believe that a few additions would make it a little better.
Bait Buckets
These would be items that could only be found in sailors chest, making them worth more than a few pennies. They would come in 3 different rarities (Common to Rare), and would be a stackable item. Going near a body of water with the bait bucket and using it would cause you to toss it in, increasing the chance of getting that rarity. It would only last for 10-15 minutes, and would reduce the grind for specific fish.
Better Catching Visuals
Update the visuals a little bit. Currently, they look pretty bland, with the fish just appearing out of no where. Maybe have it show other fish swimming around the pole before a fish finally bites down. With treasure bags, you can just have it float by and snag onto the hook.
Sharks Give Shark Teeth
Self explanatory. After fishing/cooking a shark, you would get teeth. Gives them more options to be obtained.
Throwing Net
A giant net that the player tosses into the water. It would be uncommon, and it would come from sailors chest, but could rarely be sold by Shell island’s fishmonger. It would allow the capturing of 3-7 fish at once. It would be harder to get rarer fish and items, but it would only have a 5 second cast, allowing near instant catches. It would have 3 uses, with a 1:30 minute cooldown after use.
Reason
Would change the currently mind numbing to a more enjoyable, easier experience.