So, I've been giving this a lot of thought, lately.
One of the main reasons why I struggle to remember a lot of Gen 6 and 7 Pokemon is because my mentality when playing the games was to use as many of the Pokemon I was already familiar with as possible. Unfortunately, this meant that since I was already comfortable with using a lot of the older Pokemon, I didn't give a lot of newer Pokemon a chance. I skipped over a lot of them and continued using a lot of the "old" Pokemon.
Now, don't get me wrong -- In gen 6 and 7 I've used some new Pokemon, so I didn't ignore all of them, but... even so, it wasn't enough and I stuck mainly to the oldies.
That all being said, I honestly wouldn't mind, for the first time ever (at least, since Gen 5), going through a region with completely new Pokemon with a completely new experience. It should feel refreshing, I think.