I'm going to be blunt, this really should have been two cours. For a shounen anime to end right after the buildup to a main part with no real sense of what's coming next, it doesn't really help to build the world or future for the series. So as for now, it seems to just simply be a manga advertisement.
The characters and pacing was absolutely phenomenal for the single arc, but the problem lies that the story isn't really fleshed out. We're given stark details about the world that are never really seen or put into practice. The moral dilemmas inside of the compound seem like a taster of what they would need to prepare for outside the walls, yet we never get to that point. Since I've been watching simultaneously, I'd compare it to S1 of Boku no Hero Academia. Both are 12 episodes and Shounen, but BNHA focuses first on the admission of the main hero, which sets the tone and then followed it up for a presentation of the villains. Villains were hinted at in the first arc, but never the focus. It seems The Promised Neverland would have been better served focusing on the plans of escape at the first part, then flesh out the demons world in a second similar to BNHA. The second section is important for investment, because while the first tone setting arc sets up the spike, the focus on the threat of the second arc would be the point to drive home "why I should keep watching/reading".
This is the sad part: I enjoyed what I watch but I felt no investment to continue with. I mean I can wonder what happens, however, I already know how they operate and ending it there just leaves it open ended enough to where if this had been just a bit more horror based I could have been completely satisfied with it. The knowledge that they live again to fight another day? The escape isn't so much of a spoiler, since there's plenty of twists and turns along the way, however the success of it makes much of them moot without a follow up.
If this show gets a Season 2, for all I know it could recover astoundingly and be a best loved series. However, with the lackluster end and no carrot to string anyone along, I really feel this season falls flat without supplemental materials that we honestly shouldn't need.
