Megaman 10 confirmed

[Ton]

But even despite this, they have managed to weasel in character plotline and emotion. She is solitary, she is somewhat vengeful, and she is individual: she is strong. but she is also somewhat caring; this is expressed in the ending for Metroid II by her keeping the baby metroid alive and sort of "protecting" it, despite her mission. And that's all she has to be.

That isn't to say, again, that there is no character development: there is, in both super metroid and metroid II, and in fusion and kind of zero mission. Zero mission creates a backstory of her being raised by the chozo as an orphan and imbues another level to the plot without actually relying on conventional narrative.

Does she? Or is that what you're projecting onto her? There's a difference between not giving the audience information to make the character seem detached and distant and not giving them information because the character has no information to give/you don't know how.
You can argue that "actions speak louder than words" but only if the actions have something behind them. And you are the one controlling the action most of the time.

That's not to say that I don't buy the "Samus is hardened, but cares about some stuff" angle, but backstory is not characterization. Characterization is how they react because to their backstory. Why is that backstory important? "I was born half vampire so I kill werewolves" tells nothing of my motivations and thoughts. Only where I'm from and what I do. We know Samus was raised by Chozos and is a bounty hunter, but what drives her? We can infer that it's the death of her family, but since she's a bounty hunter by profession, it could just as well be the money. We don't know. Maybe she cared about that Metroid at the end of Super Metroid, or maybe she just saw it as a lucky break and immediately moved on. We don't know (do we? I'm not sure about that example).
The fact that we only hear reactionary clips from her, like shouting and screaming doesn't help. And she's alone, so she has nobody to bounce her thoughts off of.

Samus doesn't need some epic story (though I'd argue that chasing down the space pirates, eradicating the metroids, and blowing up planets is pretty epic), but it'd be nice to see what's going on behind the helmet.
Speaking of which, none of this would matter much if Nintendo had decided to just make her some robot. But we know she's human. She has a face. Fans care about her and her mythology, but in classic Nintendo fashion, they don't.