Ooo boy, Anon, you are gonna make me write an assay. I am also pretty sure I know who you are, so I'll try to keep this as spoiler free as possible.

Before we get to *why* Umineko ladies are so good, let us talk about why Umineko's characters are good in general. For the most part, with few exception, all the Umineko characters aren't two dimensional blobs of human flesh that are "personality traits, background flashback  explaining personality traits".

All the Umineko characters, with some exceptions, are complicated human beings, who have nuance to them. These characters are all so human- for better or worse. They are both endearing and horrifying people. They act differently with different people, they have deep rooted fears and wants that they themselves don't recognize, or when they do they have mixed feelings on them. They are not defined by a simple background- but a myriad of circumstances and relationship that shape who they are.

So with that said, this is especially true with Umineko female characters. Characters like Natsuhi Jessica, Rosa, Eva, and even Maria are defined by a myriad of different things- their expectations, dreams, their familial relationships (a big one really), the era in which they grew up in, their goals, their deep seated fears, their circumstances changing, time, etc. They aren't defined solely as companions to the male characters, and in fact a lot of Umineko revolved around its female cast instead of the other way around. But that doesn't mean that the Umineko female cast is this monolith of "strong independent woman who need no man" as it were- like I said Umineko characters are defined by so many things that even their relationship to the male cast and the other female cast members  is just as valid as everything else to explore who they are.

The most important thing is that the female cast has their own agencies that motivate their actions, but that those agencies aren't always in agreement with   other female characters and male characters.  Their is friction and conflict because like I said the female cast consists of individuals, not some monolith of "cute girls who good or bad people" .And the best part is that the Umineko females aren't this perfect personification of some quirky trait or idealization of what a woman should be- they are these imperfect humans with both noble and ugly sides like a real person.

I think it just that Umineko's written to make the female cast just *actual* people that are not defined solely by their gender and personality traits, but that doesn't mean their gender isn't a big part of them either.

So, really it is less that Umineko female cast members are written in a way that sets them apart- it just they are written in a way that any character, female or otherwise, *should* be written. Ryukishi07 may have problems with his prose, but the one thing he excels at his writing fantastic characters.

The only sort of other work that I know that does this in "Anime" medium, but not as strongly as Umineko, would be  Gintama or recently certain Chaos;Child characters.