
SO, one of my favorite characters is Porsche, a centauress warrior from the thirty-first century who populated many of my first tranche of as-yet-unpublished science fiction stories. (I think she only appears in one published story, "Stranded" in the anthology of the same name, and even that, just as a cameo). And while I have worked a lot to improve my art, I wondered what Midjourney could do. And I got the above result from the following prompt:
a centauress with long, rich curly purple hair, very beautiful, with half-asian, half-english appearance, and pointed ears, wearing an armored space costume like a combination of ghost in the shell and star trek, and bearing a double-bladed scythe with black glowing blades
- the Centaur
Wow. This is really spot on. Her hair is right, her face is right, her skin tone is right, her armor is right ... heck, even her slightly haunted look is right, and to go beyond even that, one of the variants looks like a slightly older, more grizzled variant, which completely checks out with her storyline:

Kudos to you, Midjourney, except ... she's not a centauress. She's just a person, a fetching one, I admit, but not a half-woman, half-horse creature with the pointed ears and black twin-bladed scythe of the prompt.
Well, shoot. What if we look at some of the other variants?

This one is creepily good in a sense ... it's got her forehead dot (she's a First Contact Engineer, and wears a pheromone bead she used to communicate with a scent-based alien hive species) and even hints of her mechanical arm and possibly ear. But this is just coincidence. Look at this other variant:

What appears is just chance. Here, her ears are rounded, the dot's gone, and the weapon looks even less on point. A lot of what looked right to me is just random features onto which I was projecting, like cloudbusting.
Well, double shoot. What if we refine the prompt? What do we get?
a centauress (a creature with the upper body of a woman and a lower body of a horse) with long, rich curly purple hair, very beautiful, with half-asian, half-english appearance, and pointed ears, wearing an armored space costume like a combination of ghost in the shell and star trek, and wielding a scythe with black glowing blades
- the Centaur

Yerk. That's ... just jumbled nonsense. Tweaks to the prompt to make it simpler just produced women on horses. Midjourney does not apparently understand the concept 'centaur' in any meaningful sense. I tried just the prompt "centaur", and ... um ... yeah ... no, I'm not going to show you those. They're just a guy with a horse, or sort of on a horse, or ... sort of ... in a horse? A centaur as envisioned by The Thing.
Okay, one last try. What if I give it one of my pieces of art, and then ask it to render it anime style? Let's hold that piece of imagery till the last, but the prompt is:
an anime style centauress with purple hair and a double-bladed scythe jumping in front of a waterfall
--the Centaur

Oh, lordy. And I'm not going to show you the one it tried to generate from the prompt "anime style".
Oh wait, I am!

Wow. Evocative - the top left reminds me of Cinnamon Frost - but it has little to do with the image I put in, and the attempt in the top right especially is nonsensical.
I am inspired by Midjourney. It's definitely a better renderer than me, and has good ideas about composition which I have already used in my artwork.
But I stick by my comment that it is an amateur which has taught itself to render very well, and cannot take meaningful art direction. As limited as I am, I'll stick with my own drawing, thank you!
Like this one, the image I gave to Midjourney above. It's not perfect, it's not well rendered ... but it is mine:

And she has four legs, a scythe, and pointy ears, dag nabit.
-the Centaur