I created a creative world to build this iron farm (by Wattles) and see if it would work. Literally a brand new world, no gamerules are changed. The villagers aren't scared at all. I broke the zombie free, and it would go and attack the villagers, but they would just stand there and not even run away. Literally would just stand there and die. Whats going on?
I'm in 1.16.4 and the only mod I have installed is optifine (which wouldn't change anything).