"Sevmek" by itself can be either "love" or "like" (and it seems to me that it's usually more like "love"). "Çok" is an added intensifier, and that needs to be translated into English, too. So you end up with something like "I love everyone very much" or "I love everyone a lot."
Why is "I like everyone very much" marked wrong here, whereas in another exercise "Herkes onu çok seviyor" was translated as " Everyone likes him a lot?" In a response from a moderator below it says, '"sevmek" when used with people, unambiguously means "love"', in which case Duo's translation "Everyone likes him a lot?" must be wrong. Help!