It's a Halloween event. You can spin all the in-game lore you want, or apologize for Riot all you want, but the fact is that the ball was dropped, hard.
Riot needs to hire psychologists, who can tell them things like this: loyalty is developed by developing positive associations with happy times. Watching a baseball game with Dad? Eat an Oscar Meyer. Enjoying the Superbowl? Drink Coke. Enjoying a nice Halloween Saturday with friends? Cry and rage that Riot doesn't care about you or your fun.
You can say all you want, but the feelings are real, and as far as I can see, posters have come out in full force to let their feelings be known. Not even a great game like LoL will hold loyalty if these feelings get repeated more than once.