I'm not sure yet, but this is my guess. Humanoids are going to be reserved mostly for PC species. Orcs are now a PC species and won't have a fixed alignment. If there are other humanoids in the MM, they won't have an alignment either. The monsters that changed type will fill that "slaughter on sight" orc role, though with a little more nuance to their reasoning. Goblins are malicious fey. Gnolls are Abyss spawned locusts. Werewolves have abandoned humanity. Etc.
I'm very interested to see where they are going with this. I feel we are missing some nuance yet.