Despite now spawning in the major Raids spawned by walking into a village with a bad omen, witches still aren't hostile to villagers; merely occasionally accidentally having its potions hitting villagers as it attacks the player.
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The player currently has no incentive to kill witches in raids, meaning they can set up a very abusable emerald farm involving the raid mechanics. If at least one mob is remaining, more and more waves of illagers will attempt to raid the village.
Witches would be easier to use to set up said farm than other mobs, as they do nothing to prevent being trapped.
You can use mods to make them attack
This is not a bug, witches are only in raids to team up against the player, not the villagers. Witches were designed and intended to be passive toward villagers, just because they are part of raids now does not suddenly change their behavior toward villagers.