Because:
1) Voice acting in Zelda doesn't is not the focus and there's so little of it, facial animation in Horizon are not the focus but rather monster hunting. Mass Effect is a game that emphasizes on conversation and interaction, unlike those two games you'll spend half of your play time talking to people and as such it's very important here.
2) Horizon doesn't have actually bad animations, it has wonky lip syncing that feels off at times but that's about it. The eyes, head, hands and body look and animate well and you won't find complaints against them. And compared to Mass Effect it's a master class there.