1st, Natsu was the only character who got motion sickness from rides because he only rode animals when Igneel raised him, only for it to then become a trait shared between all Dragon Slayers of every generation; Igneel was shown talking to a fairy in an earlier chapter hidden in a volcano, only to be changed into being inside Natsu and dead all along; and finally, God and Demon Slayer magic being introduced, when Dragon Slayer magic requires to be taught directly from a dragon, yet we never see the people using the other two types being taught or related to gods and demons (Gray's father gains that magic because he was reanimated by an evil wizard, but then passes it down to Grey like it's nothing. Only Dragons need to spend years teaching, it seems, which would make it really inefficient compared to the other two).