So what you are saying is that it is a realistic representation of the real thing.
Not at all. The entire act of fishing is reduced to clicking a button on an almost completely static game object, an extreme abstraction, and you get bites far too often and too quickly to be even remotely realistic.
An incredibly low success rate when you do get bites isn't particularly realistic either, despite what one might assume. It's not uncommon out on the lake or river to pull in several fish in a row, and this requires only baiting the hook properly and experience handling rod... neither of which have much of anything to do with "dexterity." It's all a matter of experience. Someone's arthritic grandpa who couldn't thread a spaghetti noodle through a hoop earring could most likely still handle a fishing rod just fine.
Basing fishing success arbitrarily on Dexterity because it's "the stat that seems like it should go along with it" to such an extent that if your DEX is 5 you'll almost always fucking fail, while if it's 7-8 you'll almost always succeed, is clearly absurd.
Funnily enough, I've seen not a soul complain about this other than myself.