Ideas alone are worthless.
value = idea * execution. The best idea with 0 execution has a value of 0.
The reason is that nobody can tell if an idea which only exists on paper would be a commercially viable game. Not unless it's something formulaic which guarantees moderate sales if you throw enough budget at it. But everyone can come up with a concept for yet another first person shooter, GTA clone or grindy MMORPG. They don't need you for that.
If you have a novel idea, you have to prove that it will work. And the only way to do that is by actually turning it into a game and showing that there is interest.
- Create a playable prototype. It doesn't need to be pretty, it doesn't need to run well and it doesn't need to have much content. All that matters is that it demonstrates what's new and special about your game idea.
- Publish it (as early access alpha for money if it is worth it, or for free if you have to)
- Generate lots of hype and groom a community
- Make it apparent that people like playing your idea and would be willing to pay for it if turned into a game with proper production values, but that you lack the resources for developing it
- Get into contact with publishers
There is quite a long list of games with niche game concepts which started as small indie games and then got bought up by larger publishers after they had shown that their wacky idea has market potential.