ccs
41st lv DM
I think part of it is that so many monsters were invented during a 5 alignment system (LG, CG, N, LE, CE) that it would be interesting to see a campaign that doesn't have those particular monsters.
For one thing, many dragons (all the standard chromatic/metallic 10, for example) wouldn't exist. That puts a different spin on things.
What makes you think this? All that'd really happen is that all those monsters which have one alignment now would just get a different alignment.
If you don't believe me? Just look at previous editions of the game.
Or ask those who play with no alignment system. I bet they still have red dragons etc....