The thing about first-person novels is that they have a higher degree of difficulty. Certainly, they can done well, but they're easier to screw up as well. David Hartwell, who was one of the original TrekLit editors, once advised young writers to stay away from first-person until they were more experienced. At the time, I was young and mouthy and debated this point with him, pointing out umpteen classic novels and stories that were written in first-person. David conceded their existence, but still maintained that new writers attempted first-person at their own peril.
Like I said, I disagreed vocally at the time, but, three decades later, after having waded through way too many slushpiles, I see his point. First-person contains many traps for the unwary . . . .
1) The narrator can come off as indistinct compared to the other characters, who can be described in vivid detail. Indeed, having a narrator describe themselves or their expressions or body language is always problematic. You can only have them look in the mirror so many times . . .
2) In my experience, first-person makes it easier for the author to indulge in long-winded internal monologues, perhaps to excess. It's easier to get carried away with that sort of thing when writing from deep inside the narrator's head.
And speaking of long-winded monologues, I've clearly thought too much about this over the years!