On that logic, Iron golem farms are cheating too. Im getting Iron by doing nothing. I am not even holding a fishing rod or anything.
Again, that gear is mostly worthless junk with worthless enchantments. You don't even get enough levels to combine everything easily anyways.
Also, so what If i get a bow or some leather shoes? What Do I gain from that? That doesn't build me a base or build a mob grinder.
You can't get anything made of diamonds, iron, coal, or red-stone from AFK fishing.
Someone would have to be a real idiot anyways to trade with a villager for those items anyways.
Mostly. You're utterly ignoring, either on purpose, or by ignorance, that Mending is included in the enchanted books, on top of potentially getting other high-level enchantments. As for "Worthless junk with worthless enchantments", that's a rather weird way to call a bow with Power, at the very least; or a pre-enchanted rod (I don't AFK fish, but every Mending fishing rod I've got has come from fishing).
You cannot get diamond gear by AFK fishing, but you can make it ever-lasting with it, without taking effort beyond putting a weight in the RMB and moving on to do something else.
Iron Golem farms at least are a logical result of the presented mechanics. AFK fishing not only doesn't make sense, but essentially uses unintended behavior in order to allow something the game doesn't allow at all otherwise. Particularly telling is that, otherwise, there's no way to farm for fish without right-clicking, and that part of the way to do so involves PUTTING A WEIGHT ON THE RMB, which is something the game doesn't promote otherwise.