Honestly...I found Sun/Moon the perfect difficulty with my style of play. Like usual, the game can still be mind-numbingly easy, but I've created a few rules for myself that not only make it more challenging, but more fun to play overall.
-Don't grind unless absolutely necessary
-Turn off option to switch Pokemon after opponent Pokemon is defeated
-Turn off Exp. Share (I use this a lot in the post-game, but it massively over-levels your party during the main adventure)
-Don't be limited to a party of six, and don't force myself to keep everyone at the same level. My last playthrough, I had a party of 15 or so Pokemon I liked, which I slowly widdled down to six by the time I faced the Elite Four.
Now...these rules might not be fun for everyone, and it's admittedly an excuse, since some of these options require you to go out of your way, but for me, they helped keep the experience fun throughout the adventure.
That being said...a difficulty option is always welcome.