90% of the fanbase became a hatedom until the manga came around with explicit exposition.
Took a while to 4chan to come back to be a “positive” (mostly) fandom again, more or less in 2015, but it happened pretty nicely (many anons started pointing out all of the explicit info were in the Visual Novel all along and people finally started to see Umineko the way it should be seen).
But there’s still hate (just a bit), since some people got offended with the Goat thing somehow.
Animesuki forum tab for Umineko went retired before that thing happened, but people already didn’t quite remember stuff when the final EP8 chapters were released, so they mostly dismissed it as a retcon and the thread is pretty much dead now.
You missed nothing, only a terrible time period…
Shkanon was increasingly becoming popular after EP3 and was accepted to be the answer by EP6 when it became just obvious you just can’t solve it without assuming that Kanon = Shannon (especially with the Red by the end of it).
“Fucking Moon-chan!” (Jessica) was more of a meme culprit, much like Magical Gohda Chef (but both of them had quite elaborated theories surrounding them… though by EP6, they kinda got discarted and became a legit meme status for good).
There were also tons and tons of joke theories, and one of them, hilariously, actually was correct in a way (The Pony Theory).
There was also the famous Rosatrice theory (contrary to popular belief, it only really became a thing after EP8 came by, it wasn’t quite an established idea before that, as people just hated George with an absolute passion and treated it most of the theories involving him as jokes (Fat Jooji, white cucknight, and so on)). As he is a big part of that theory, it only really got the attention of anyone at all when this crazy KnowNoMore user uploaded an 8-hours long Umineko theory to youtube trying to prove his point. After the manga release, he deleted the videos, but some people reuploaded them later, for history sake.
Besides that one, there were also many meta theories from EP2-EP7 (EP8 pretty much confirmed one of them by the end of it while denying all of the rest, or at least most of denominated correct theory was actually right, as Battler’s body was still alive and stuff, while in the suposition, it should have been blown up with the island).
Good and fun times, I could enter in details about some others, but they weren’t quite as relevant and/or elaborated as those from what I recall. I’ve been in the Seacats fanbase theorizing with everyone since Witch Hunt made their first release, and I must say:
Besides how toxic and completely chaotic every single Umineko related thing became (it was one of the biggest things in the whole japanese-related 4chan for YEARS, be in /jp/ or /a/), those times were absolutely one of the most entertaining times I’ve ever had debating about a work of fiction. I hope with all my heart this happens with WTC5 as well (and of course, also hope that it doesn’t end up like Umineko: being hated by everyone for quite a while and all that).