why you keep pulling up trash
Junk is the game telling you the setup is not good enough yet. Two checks decide it: whether the pool counts as a proper lake rather than a puddle, and whether your fishing power has cleared the bar. Fail either and most of what surfaces is worthless. Fail both and it is nearly everything. The three junk items behave identically, so which one bites is cosmetic.
fixing it
Widen and deepen the pond before you blame the rod. Plenty of people fish a puddle with a good pole and top bait, then wonder why nothing bites. Once the water is large enough, pushing fishing power up with a better pole, better bait, the fishing accessories, and a potion clears the second check. A Blood Moon rewrites the odds: junk mostly stops, but what takes its place is enemies on the hook.
worth keeping now
It used to be pure vendor filler. These days an Extractinator grinds junk into low grade bait, which closes the loop for anyone stuck early with a bad pond and no worms. It stacks high enough that hoarding costs you nothing. Now and then the game hands you a Joja Cola instead, worth just as little but at least a joke.