The classes have completely different expectations of players stats, you realise. If fishing actually expected BTN/MIN tier stats it'd be impossible, but it doesn't - the stat cutoffs for catching fish are based off of what a Fisher can actually get.
1) They aren't actually that much different; highest BTN/MIN items requires 420 gathering, highest FSH item needs something like... 407, 408? It's a LOT less than the difference an offhand would make.
2) As such, BTN/MIN can easily get everything while still far below their stat caps

Not so with fishing. Come back when you have BTN/MINs doing things like taking i70 DoW/DoM accessories and melding those instead simply for the extra one point of gathering/perception each, milking every little stat point they possibly can, and STILL struggling to obtain their items.