Agreed. You have to be prepared for the slaughter-house, and you have to possibly accept the cruel fact that people aren't going to see what you see. You may have a wonderful idea, but it's such a slim market for getting things into the gaming industry. Aside from the fact that it costs less to take ideas from the inside, it's also less of a liability. And perhaps one of the most important reasons is that many ideas are collaborative efforts, especially in smaller studios. Lots of minds will come together to hone in on one particular idea out of hundreds of ideas that are brought to the table, and when this is the case, you have more people who feel like they've had a part in the idea and thus feel passionate about it. When you get an idea from the outside, people might like it, but they feel like they've had nothing to do with its origin.
I would again recommend submitting to a publisher rather than a developer. If a publisher decides they like the idea, they can fund it and get someone to work on it. If a developer likes the idea, they have to get the publisher's approval and proper funding, get the team on board, etc. That's if they aren't working on something else which they most likely will be, and if they are receptive to unsolicited material which they most likely won't be. IF you submit to a developer, I recommend submitting only to those who have an open position for a Writer. Yes, there are a few out there that do hire writers specifically, and they might be far more receptive to possible freelance work for that project, or you might just get a job out of it, and then even if you're not working on your ideas right off the bat, you have a far better chance of getting your ideas seen.
One more option is to get your ideas into a visual format. Try and get together a team of amateur designers to make a demo using your materials. Game development students are great for this because they will be getting team experience for their portfolio, and you'll be getting a team to bring your ideas to life. Why bother with this? The truth is that anyone you contact in the industry is going to be busy. Usually too busy to read through pages and pages of material, no matter how great it is. So if you make a demo out of said material, it's much easier to access in a much smaller timeframe, and it's also quite impressive for your future developer to see what they might be working with, and to get the idea that you're really serious about your ideas.
If in the end you do all of this and still no one bites, don't consider it a faikure. You've turned your ideas into a running game! And that's worth a lot to the industry. You can take that demo and then present it to the same developers you tried to sell the idea to originally and then try and get a job, and you'll be much more likely to land inside, and from there, as I said, it's a great deal easier to get your ideas heard, especially if you're working on the design team.