Luke got help from Obi Wan to blow up the Death Star, and he got a couple months of training from Yoda before facing Vader in Ep5, whereupon Luke was soundly defeated, losing his hand and jumping off the catwalk to escape.

Rey has no training with lightsabers that we see and defeats Kylo Ren in her first fight.

Maybe Rey has to be a Mary Sue... because Sexism.