There's a difference between having no idea what you're doing, and not being able to figure it out and do it.
Back in my consulting days, I never once went on a consulting engagement where I really knew what I was doing. But within a week or two of starting, I knew enough to do it better than some of the client's employees. Within a month, the job was well understood and quite boring (at which point my performance dropped back down, but not because I didn't know what I was doing).
If you know exactly what you're doing, why aren't you getting someone else to do it so that you can learn new things?