If you are so sure that you can get a good job in the private sector, put out some feelers before you leave. Worst case scenario, no one interesting responds,you can work on an idea and foundation for a startup at work.

Personally, the people surrounding you should not be the reason why you are frustrated or enthused, it should be about the work. If the work is getting you down, talk to your manager about what you just said to us. I think you will find that he will be most interested in maintaining a capable individual and find many opportunities for you to do fascinating work, on a higher level.