Why won't publishing houses treat published authors (by that I mean published by top houses such as Penguin Putnam, Harper Collins, Houghton Mifflin, etc.) different than slush?Have you ever read something by a very well-known and well-respected author and thought, "How did that get published? Sheesh, some of his/her books have been great, but this is tripe"?
Aha. That's nothing compared to the ones that aren't getting published.
One of the most surprising discoveries young publishing professionals make upon finding a chair on this side of the desk is how many well-known, well-respected authors are totally incapable of telling when they've written something good and marketable, and when they really, really haven't. I have personally rejected dozens of manuscripts from an author I thought the world of when I was a young reader. Now I know how many ideas he/she goes through to find one that works.
Should a published author try to get an agent even if they would rather do the submitting themselves?Ah... maybe? One of the best things an agent can offer you is his/her contacts within the industry, which is why he/she does the submitting. But maybe you have contacts. In that case, an agent also offers you an insider's understanding of how the industry works, what to look for in contracts, and can be an intermediary when you and your editor disagree strongly. If you can find an agent whose personal style suits you, an agent can be a tremendous blessing.
Is it foolish for someone like me to still be submitting through the slush pile and resisting getting an agent? I have heard things about agents that make me wary.Not foolish, no. But my advice would be to look hard for an agent-- one who suits you and your needs. You should be wary--there are some agents who are No Good. And there are other agents who are Fabulous, but who would be No Good for you.