Gen 6 is replayable, because there are only a couple cutscenes here and there and the rest are in-game interactions like in the older games. For example in XY you walk through the forest early on and Shauna comes up next to you, walks over to a bush, gets an item and gives it to you. You move on right away, there is no cutscene you load into and back, the moment is just part of the actual game. There are very few longer cutscenes like the one where the ancient weapon gets destroyed.

In Gen 7 basically every single interaction no matter how irrrelevant gets it's own cutscene. You are watching a movie inbetween playing Pokemon and it's not a good one. They more you replay it, the more draining the games become unlike any other Gen before it. After 4 runs through SM & USUM combined, I will probably never replay those games ever again. It's hell.