A lot of the low star reviewers CLEARLY didnt watch the show with any level of attention to detail or need to rewatch.
Rewatching the show presents PLENTY of opportunity to understand the hidden plot and the person I'm viewing with who's watching for the first time with very minimal hinting started connecting dots and figured stuff out long before the anime reaches the breaking point of slapping you with the info. (which most have dubbed a twist)
That being said, there is little in the way of actual LORE/story telling. This is ALMOST like a game of Clue but instead of finding a murderer and how they've done it you're finding out what is going on in a Truman Show-esque Kill Bill inspired gorefest.
There was no twist, you just missed every ball thrown at you.
Potential spoilers to point out a few missed hints
The dads not a creep- HES NOT HER DAD
So him being blatantly weird but never being directly sexual or explicit was a SIGN
Her food is dosed. She gets STATEDLY different coffee and and her candy is later revealed to be literally made of blood.
Interactions with her and her "friends" are VISIBLY fake.
People, this show had a team behind it. These interactions dont come off as fake for no reason.
The town is EMPTY and is stated as such more than once. People. If the characters themselves are saying its weird. Its probably weird.
"There's one of everything" remark during a conversation between the characters. The conversation CLEARLY being pointed towards the fact that SOMETHING isn't right about the WHOLE ISLAND.
The only leniency to be had for people is that the shows very short. Given more time to sit down and think about clues people maybe could guess more easily.