When trying to explain Agile to the people, did you think that maybe they didn't do waterfall in the past anyway?
If you use in any cases the classical explanation of what Aigle is about by opposition to a waterfall process it could be a good idea to think if they know what you are talking about. Maybe because they are very young and their first job was actually in a quite agile company, for example. Or they don' t know any other reality and so don't see any disadvantage on it.
Whatever it is the reason, when we explain what we do with teams or the value we can create, it can be a good idea to think about what we do and want to help the team achieving more than in what we don't want.