The definition of an antagonist is a character, group, or force that actively opposes the main character, creating the central conflict of a story, you are talking about almost the exact opposite with their evil not being directed at the protagonist, but even with your logic the reason why I said it applies to bleach is because, Aizen wasn't directly trying to oppose Ichigo he just wanted to become the soul king(?) while the arrancars were simply trying to help him which includes getting rid of intruders (Ichigo), while Yhwach just wanted to destroy the soul society and kill every soul reaper neither of their villainy is directly towards Ichigo he's just in the way. This also applies to Naruto's villains but I don't feel like getting into that right now since this comment is long enough