Bouncing idea sis one thing, but the moment you start letting an agent say what you should or shouldn't write, you're no longer a writer. I doubt there is a better way to kill a career, or, at best, have a mediocre, midlist, or lower, career.
Editors, on teh other hand, generally give advice after you've decided what to write all on your own. This works.
I think that's a bit severe. Agents and editors have vast experience dealing with the market, and have developed a sharp eye for spotting problems that the author probably can't, due to being too close to the story for prolonged period of time, thus losing objectivity, as well as having possible personal biases that result in blind spots. They might notice plot holes the author didn't, or recognize eyebrow-raising personal biases, or even common cliches in plot devices and character development. The vast amount of critical judgment they have to do on a large number of books throughout their careers, as well as their knowledge of the market, is a valuable resource that I think authors would be wise to utilize.
We have all read books and watched movies/TV shows that made us think, "Geez, it looks like the writer didn't even discuss the story with his agent/editor/director/producer, because it's full of plot holes, inconsistencies, cliches, and annoying/frustrating personal biases."
I'm not saying writers shouldn't do their best to work those problems out on their own. What I'm saying is it's smart to take advantage of the sharp, critical eye of experienced agents and editors, because they know things you don't, and it would be arrogant and foolish to think you're above them and that they have nothing to offer you in the form of helpful critique and suggestions.
Obviously, you have to draw the line somewhere. If you are completely spineless and would buckle at the slightest criticism, then you probably shouldn't be a writer. If you know for sure that you happen to have an esoteric/niche voice that appeals only to a small segment of the market and have no hopes of becoming a bestseller, and the agent/editor is trying to broaden the appeal of your book by making it more mainstream, then it's a decision you have to make for yourself--whether to stick to your guns and embrace the fact you'll likely never be a big selling author, or make compromises and take their advice.
It also sounds like you might want to explore how to find a critique group of other writers.
I'm used to be a part of a writing group back in the late 90's in San Francisco, where the members would meet regularly. But I haven't been able to find an online group--partly because I feel a little uncomfortable when it's not face-to-face with people I can see and feel their vibe. I would love to find a group of people I can fully trust and feel comfortable around, but it's much harder on the web than it is in real life. I visit the AW Chat sometimes, but people come and go, so it's never a set group, where there's a pact made between all members--a formal group of some sort. The SYW and beta resources at AW have a similar issue where it's a bunch of strangers instead of a small group of people you know and trust and feel comfortable around.
