He's disappointed because it's a bag full of uninteresting yellow discs, when he was expecting gummies. In the last panel of the page before he opens the bag he's holding it and imagining the winking gummy.
Chiefly: variety.
It's a truism that the runaway success of superhero comics pretty much killed of other genre of English-language comics. Long format American comics were pretty much all superheroes from the onset of the Comics Code until the turn of the millennium, and even now we only rarely...
I've added a few Isekai to my follows lately, mainly because I need something easy to digest after work. And frankly, the more trite, the more formulaic, and (especially) the more just plain silly, the better.
Take, for example Shingan no Yuusha...