The one thing I’ve heard about Couer is that he always puts Jaune at the forefront, which people say is an actual problem the main show has.
The thing is, he constantly writes Jaune because Jaune, sticking strictly with canon, is the easiest to write without completely remaking the character, because, as Chilson said, he has an actual multifaceted character and multiple character arcs. Couer's works, for the most part, try to hem closely to canon, only changing what would be necessary to make that fic's particular caveat to work. For example, in the work that made him famous,
Not This Time, Fate, the story of the world of RWBY pretty much follows canon without any changes. The only change is that Jaune is a time traveler who keeps jumping back in time every time he dies at the Battle of Beacon, and is constantly trying to avert the death of both him and his friends, only to constantly fail because of his inability to know all the angles, because, even though he's been repeating the same few months for
millennia, he still doesn't know all the things we the audience know from having watched RWBY, like the fact that Salem exists, because there are still some things he just can't find out. Most of his stories focus the changes on Jaune specifically as a character, because there is a lot you can do with him.
It should be noted though that he doesn't always focus on Jaune in his fics. On that note:
a relative lack of willingness to make changes to experiment with making RWBY the protagonists of his fics (which implies he runs away from this issue rather than confront it)
He has actually made Ruby the main character or a major character in his fics. Specifically, his Alternate Universe fics, which don't use the canon of the series at all, tend to feature Ruby as a prominent character because Couer can actually give her more depth, nuance, and internal conflict than in the canon portrayals, where she's basically just a bundle of hope and sunshine in the first volumes, and downright insufferable in the later ones. Specifically, she's a Tritagonist in The Unseen Hunt, one of the main love interests in Forged Destiny, and the main protagonist of Arcanum.