The omniprotagonist fallacy is the mistake in writing of treating every character as a protagonist. I've only seen this once, but it was really bothering me so I thought I'd write about it.
The book was The Grace of Kings by Ken Liu (yes, the same book that betrayed me with the worst time skip I've ever seen). There must have been more than a dozen POV characters in it. Now I have a novel with a similar number, but it's not the same. In The Grace of Kings, there were only two real protagonists. But every couple chapters I would be treated to one following a character I had never heard of. Sometimes one of the generals commanding the enemy forces, sometimes the princess of one of the islands that hadn't had anything to do with the plot yet (and never did), sometimes some random woman who happened to be a good tactician and was about to join the goodguys to help them. The author would tell me everything I could possibly want (or not want) to know aout the character's backstory, and often they would just die later without ever becoming important. It was as if the author wanted every person in his world to be a protagonist but wasn't willing to write a separate book for each of them, so he just threw them all in the same book.
Not that I think you were planning on it, but... don't do this.