5e's equipment includes fishing tackle, which seems clearly designed to enable a character to catch fish by attaching a line with a hook and lure to a pole, then eventually pulling a fish out of the water. Pulling large fish out of the water with a 'hook, line, and sinker'-type set up is not really a sure thing, and it seems like there should be a roll involved, yet no guidance is given within the description of the item itself. What do you roll to successfully catch a large fish with a fishing pole?
Why roll at all?
Because the outcome is uncertain. Trying to catch a large fish with a rod in real life is not something that most people can do without literally bolting themselves to the floor of a large boat. 5e doesn't have modifiers, right? So that step isn't a thing. What's the benefit of using fishing tackle rather than your hands/a spear/ a 10' pole? If the system is going to provide this level of detail (i.e. exceptional gear for fishing v.s. regular gear v.s. improvised gear for fishing v.s. no gear) it seems like it would require more than just advantage/disadvantage, which in 5e seems to mean a table of DCs based off of gear or something buried somewhere random. It appears no such mechanical detail has been provided so far, but something would still need to be done.
What about homebrew and 3rd party stuff?
Yes, that sounds like the right answer, since the relevant material seems to be missing from the first party books. Tested homebrew or 3rd party stuff with a positive evaluation of some sort would be a good answer.
Why not just say 'the DM or player(s) decide'?
Well, that's equivalent to not having the equipment on the list in the first place. I figured since they put the gear in the equipment section there'd be more to it than any other piece of equipment that the players could make up to buy. Sure, the fact it has a price makes it useful for disassembly into its expensive and useful component parts, but that's not usually the intended purpose of non-kit equipment. This idea does seem to have been wrong, however.