@Hanassi I read a lot of isekai manhwa and manga so I get what you mean.
A few novels on RoyalRoad by an author named Andur expanded my perspective on isekai/ reincarnator MCs quite a bit so I'll share some insight from him with you. This is due to his novels having the interconnected thread of a handful of characters consistently being Isekai'd.
Let's look at it in a different lens.
Usually in the first reincarnation or when the MC is Isekai'd as a baby, they are prone to falling in the pitfall of being influenced by their biology (the challenges of adapting, puberty, and new familial figures). The cases where we get hard-ass MCs from birth is when they have very driven personalities.
Multi-instance reincarnators have developed a more structured personality and thus are often more solidly driven when faced with difficult scenarios.
In the case of this story, I believe the MC was just absorbed in the nature of her life. Honestly, it's so tragic to have your mother die in childbirth and I think she as a child was drawn to family acceptance over independent action.
Yeah, I enjoy the stories but sometimes a bit more flavor text or character musings would go a long way in setting the personalities of certain characters.