I just finished Shin Sekai Yori (aka From the New World), a serious science fiction anime series of 25 episodes (link is to a free stream). You could almost think of it as a (more) rationalist Warhammer 40,000, except that the atmosphere and aesthetic is a lot less heavy metal and more similar to, say, Speaker for the Dead. It's a little over-reliant on choppy flashbacks but generally well executed with likable characters and very strong world-building.