Umineko, like most visual novels, is nothing special. I don't know how to say this without sounding like a cunt, but I think it's true, so I'll just say it.
Visual Novels (excluding dating sims, nukige, or other shit made explicitly for cooming) seem to play on the fact that most weebs are dumb as fuck. They're not well read, so when they come across otherwise juvenile crap like Umineko, it blows their minds.
Umineko makes almost no use of the video game medium, it's more of a "kinetic novel" than a visual novel given the lack of choices, so it's functionally just a book. But given that it's not a book, let alone a critically acclaimed one or a best seller, it's evident that it doesn't really have literary merit.
So then what's the point? Well, there isn't one. It's just a mediocre non-book. Shit like this (Nier: Automata also comes to mind) is a way for weebs to feel like intellectual grown ups because it's a step up above the high school harem booba battle shounen content they usually engage with. Yes, Umineko is better than literal garbage like F/SN, Grisaia or Fata Morgana, but that doesn't make it unique or otherwise important. It's trash to compared to actual literature, so at the end of the day it's just pulp with ugly anime drawings to entice weebs. It's a weeb thing, ergo weebs think it's fantastic and important.
It's really funny, because so many of the people I know who fellate Umineko (the ones who tricked me into reading it), would never deign to read it it was presented as an book. They'd probably laugh it off as a Sherlock Holmed rip-off for 13 year old girls.
Weeb shit + the slightest scintilla of intellectual merit = complete and total weeb reverence.
Nier: Automata is a great example. The weebs playing it are uneducated and have literally no knowledge of philosophy outside of what they've picked up through pop-cultural osmosis. So when Taro introduces these laughable, baby-brain Philosophy 101 concepts in the most basic ways possible, they think they're experiencing something truly profound.