I could be wrong, but I didn't take it that he was calling for a literal belief in mythology but rather a new set of symbols to replace the old ones - while being fully aware that they are myths (non-literal symbols).
You may be right but if so then Campbell understands far less about the human psyche than he does mythology.
There is no way you can take away the literal belief from theists and replace it with non-literal mythology and have it satisfy their needs.
I have to confess, though, that I'm a little lazy for mythology anyway. I'd rather just be told straight up than to have to dig out the moral from a story. I'm more of a "Just tell me the point you want to get across" type. Mythology can add a layer of overhead that's too easy to confuse for the message - at least for me.
I like finding the moral or meaning in folklore and myth and enjoy a good analogy (a rarity) but I believe you`re right that Campbell`s idea would for the most part confuse the masses about it`s objectivity.
Considering they already seem quite confused about the reality of the current mythologies we have I see no reason why a new better mythology would be any less confusing.
We already live in a world shaped by believing and living modern myths. Where we now wallow in a chotic mess of mythic images that compell us -- ranging from advertisers promoting ideas that we "need" this and "need" that until they become a necessary, ingrained part of lives, to idealistically spending millions of dollars to send a robot to Neptune just to be destroyed, to decrying villains for their humanitarian works and exonerating heroes for their failings -- what Campbell is calling for is a particular type of myth that will specifically address a more healthy relationship with the world around us. It will describe us: take us away from the current story we've written about ourselves and all subscribe to, and inscribe us closer reality, closer to home.
I don`t recall Campbell comparing the modern myths you mention above.
In The Power Of Myth he directly confronts the problems of believing in the ancient myths and how he believes they need to be "replaced" with( as you say )something modern people can relate to in their environment.
However even if you`re correct to any extent I still disagree with him.
It`s my experience that most people in my culture have no understanding of what myth is as is evidenced by your mention of the plethora of modern myths not to mention the literalism rampant throughout Christianity in American culture.
For the average person myth can`t equate to reality and still fulfill the promises made by the myths they hold as truth now.
If a new myth based upon reality were to attempt to compete with the unrealistic promises of the old myths it would lose hands down.
No afterlife, objective cosmic purpose..etc.