The killer app of comfy UI and node based editors in general is that they allow "normal people" to do programmer-like things, almost like script like things. In a word: you have better repeatability and appropriate flexibility/control. Control because you can chain several operations in isolation and tweak the operations individually stacking them to achieve the desired result. Repeatability because you can get the "algorithm" (the sequence of steps) right for your needs and then start feeding different input images in to repeat an effect.
I'd say that comfy UI is like Photoshop vs Paint; layers, non-destructive editing, those are all things you could replicate the effects of with Paint and skill, but by adopting the more advanced concepts of Photoshop you can work faster and make changes easier vs Paint.
So it is with node based editing in nearly any tool.