I'll just say it outright, but there's a lot of misconceptions about past humans and cultures, especially that of medieval Europe. (For example, witch hunts /did not/ exist during the medieval period - they began after the medieval period around the 15th century and continued for multiple centuries forward. It's just easy to imagine medieval Europe as some gruesome, inhumane place, which is why there are so many myths and misinformation associated with it.) I mean no offense, I'm simply a history nerd who wants to share the truth of what I know and correct people on the misinformation we've all been taught.
Like I said, people have always been people. We've always built communities around us and taken care of each other. This doesn't change throughout history. There are gruesome moments (typically fueled by the idea of us vs them, and thinking of the other people as lesser than your group), but for the most part, this is how it has been. There are shitty families and I'm sure there are communities or sections of culture that have acted similalry to the series, but in no way has it ever been mainstream enough to call for such a broad time period and area. (The area of Europe has never been a monolith, even if it has been told to be so by the standards of "western culture" and "whiteness".)
But yeah, I feel you on the first part. It could be that it's partly bc FL doesn't really seem traumatised and treats her pasts fairly lightly, making them seem less harmful. It could also be bc the abuse has been mostly emotional neglect (with some material neglect), and while neglect is still abuse, it's def more forgiveable than those stories where the family physically and/or mentally abused the MC/og body (that traumatized them super bad) /general mistreatment but still get forgiven.
Also here the brothers are more easy to forgive considering they were children as well for the longest time.
+ yeah this is a fantasy world with magic, c'mon, the races of people are based off on animals. Different standards ig, although I don't like this reasoning too much bc it was still a choice made by the author ┑(￣Д ￣)┍
Also, I do realise you specifically mention the 1600s, which is great considering Europe was def not the best place around the time (witch hunts were def still a thing). I just mentioned medieval Europe since most people tend to refer to that with these stories despite me only knowing one historical manhwa that really feels like it took inspiration from actual medieval Europe (Under The Oak Tree) (￣∇￣") for those who read this who don't know, medieval Europe is a time period roughly between the 400s and the 1400s - and these stories tend to take style inspiration from closer to the 1600-1700s.
Maybe it's because I've read a lot of stories with shitty families that I don't see this as something "wierd", It's also because I don't confuse their way of life to our modern society or reality. And I bet their culture is somewhat similar to ours in around 1600's or something. Ours might even be worse specially around Europe.