Watchmen only has "original" characters because DC made him. SpecialKO is right. He's a hypocrite. Hell 2 of the top 3 titles he's known for use pre-existing characters. Yes I mean Watchmen in that because the characters are as original as the Shi'ar Imperial Guard.I disagree. As you said yourself, there's nothing wrong with derivative works. I've argued many times before that most of literature is inspired by something that came before. Shakespeare, for example, borrowed heavily from several fellow playwrights to create his work. He stold lines almost word for word right out of travel journals for The Tempest.
There's nothing wrong with taking something and being inspired by it to create your own thing. Watchmen and the Charlton characters are very different. Watchmen grew out of something different, as a result.
You can make something new out of something old and still make your product something original.
It's interesting watching Twitter, Gail Simone is annoyed at him for calling all the artists he worked with that are still in the industry worthless. Bendis is a little hurt, and Ed Brubaker is annoyed. Simone and Brubaker pointed out how full of hot air his statements were since he loudly and publicly admits he doesn't read comics today and hasn't for a long time.