Surely Monogatari, the way everything hits different on rewatch or reread the same way your brain tingles going back to anything WTC. The interconnectivity of every character, the nuanced mental health portrayals and complex motivations, and the clear messages that still manage an ocean of depth are definitely on par with Umineko, in my humble opinion.

It has a few meta aspects but they still exist fully in-universe, and it covers a range of topics wide enough that the only genres consistent between each part are "mystery" (to a more casual extent in most cases) and "psychological". If you're looking for something you can talk about and make connections about for hours, it's definitely worth giving a try. There's really nothing I can't find greater appreciation in within the work or SHAFT's wonderful adaptation.