Someone has to be the bad guy. Antagonists add to the story. A story without struggle and loss is boring, hero's journey and all that.
Well, now you're in my bailiwick, throwing Joseph Campbell in to this argument/discussion.
In many cultures and times, the "Hero's Journey" doesn't entail fighting anyone except perhaps the weather or the landscape. It has nothing to do with external conflict - it is an internal, spiritually maturing journey.
"Someone has to be the bad guy" is only in cheap and/or bad fiction that shows little understanding of Campbell's work.
Tell me, in Hemingway's "The Old Man & The Sea," who is the "bad guy"? Who is the "antagonist"?
I can toss a couple Jorge Luis Borges stories at you, or perhaps some Maya Angelou or Mircea Eliade to underpin and illustrate my point. Also a bunch of Native American or Inuit stories. I might even be inclined to toss Robert Graves at you although his work is riddled with inconsistencies due to his personal prejudices.