There’s really not much suggesting either way whether or not Wookiee language is easy or hard to learn, so I’d personally take Rey picking it up as evidence that it’s easy. Not as evidence that it’s hard and that she’s OP.
I never said it wasn’t easy to learn; I said that it was implied to be rare, in that Chewbacca is the only Wookiee shown outside of his homeworld and most people do not even know what a Wookiee is, let alone its language.
Regarding the thing in the later part of your comment about faith, that doesn’t explain how Rey knows how to resist Kylo’s mind probe or how she knows how uses the mind trick. This is what people mean when they criticize Rey’s usage of the Force without any training.
Also, a single-handed sword-like lightsaber with a weightless blade that can kill you if you were to use it incorrectly is not the same as a heavy-weight double-handed metal staff.