Considering that the availability of hyper potions, the HM Fly, and other high tiered items are unavailable at this point the Cotton Candy is not something to go ballistic about and is a good idea. In reality the game is already far into it, we have beaten 12 out of the 18 gyms, so more than halfway. The addition of the Cotton Candy item was perfectly OK in story and progress terms since there are no max revives to date.
I am a half casual half strategist, main focus is to go straight for the kill. But I get engaged in the story if it's a good one so I can be in a rush at times. But if that doesn't work right away Cotton Candies are right up my alley to get my team going. It's not as if the item gives you an insta-win; it takes just as long to beat a gym even without the item, sometimes even longer. The gyms are a hit or miss in this game; either you sweep them like I did Terra's, or takes several tries to beat like I did Charlotte's.