Apparently EXP Share got the axe for good. Now, all your party gets EXP naturally.
Am I the only one who never really minded this? I was never really a fan of grinding each individual Pokémon for hours and hours, so I just kinda...left them on the back burner, and regretted it when I got to the end.
With all my party getting EXP, not only is it evenly leveled, but it saves a lot of time that I could use to actually get through the story. Of course, grinding is still involved, but not so much it just about pads out the game.
Think of it like most RPGs; Kingdom Hearts for example. All the party gets EXP, but the difference between Kingdom Hearts and Pokémon post-XY, is that in the latter's case, the party member who's active in battles gets more than the rest of the party, whose spoils are divided.
TL;DR: I liked all my party getting EXP because it saves me a lot of time and trouble, which makes it more enjoyable for me than simply grinding each individual one for countless hours.