(spoiler free, almost) umineko honestly has so many themes and messages that it's impossible to point at a specific one and say "that's what it is all about" when trying to ~advertise~ it to friends. i think every single reader can find something deeply personal in it that would either resonate with them or be somewhat of a mindset-rewiring insight. so i'll just share the 3 personal things for me in umineko, too.

as i see it, one of the key themes of umineko is sublimating emotional energy into fiction. the story features 3 people who, at different points in time, grapple with their intense emotions through writing stories - and inevitably affect others through them. this writing is dark in the hands of someone who's succumbed to deep depression, poignant at the pen of someone who's suffering and repenting, and hopeful coming from someone who's hurt but learned to look into the future. in a way, i view umineko as a story about how creating fiction can be a method for working through your thoughts, conveying feelings (when you can't do so directly), or even healing. i hold fiction in high regard and love writing as a form of self-therapy, so it's pretty obvious why this theme is important to me.

perhaps the most subjectively interpreted theme i cherish in umineko is that of the material & immaterial realities or physical & emotional loves. arguably the biggest part of the umineko's core tragedy is in the socially-acceptable belief that real love cannot exist without its gendered worldly aspects and that people who can't grant them can't love or be loved. at the same time, the story shows that any rampant material urges and desires (be it sex or money) can be deeply distorted and flawed, leading to all sorts of deep traumas for other dear people. and in a way, it ends up ~romanticizing~ the realm of immaterial for me. it shows that while being known and seen is scary and difficult, a genuine and deep connection of souls can create a new universe. and this universe is where love can become the force that lives on through time, distance, and even existential planes.

finally, the message i really love is the humans' need for self-healing. like higurashi, this is a story about how people can't carry the weight of the darkness alone and need to do something about it. like higurashi, umineko acknowledges that communication isn't always possible and sometimes someone just ends up being a scapegoat or a victim of someone's suffering. but while higurashi still mostly focuses on the importance of communication and/or even self-sacrifice (= hanyuu), umineko adds a wise message to that "scapegoat" reality. it says that even if you find yourself in a position where someone pushed or keeps pushing their darkness onto you, you can and should stop the cycle of abuse. instead of propagating darkness further or ruining yourself by wallowing in self-pity - work to purify it, turn that pain/anger into kindness and understanding.
without love, the truth - i.e. the pain of every single person alive in this world - can not be seen.

i guess these are the main reasons why umineko is important to me personally - but these certainly aren't all of the reasons, haha. but i guess just from these 3 points, it's obvious why basically anyone who read and loved umineko is an instant green flag of a person for me 😅👌