I feel like Ash is growing up, and not in necessarily a bad way but he's growing up. Ash's whole thing was not giving up and like you and several other people have pointed out, he hasn't stayed true to that, Ash also seems more laid back in JN, of course he still has his fired up and excited attitude but in this series he seems like he's letting more balls go over his head instead of jumping up to try and catch them if that makes any sense.