Just finished reading the War of Art by Steven Pressfield. Like many creativity books it does well describing the barriers and frustrations that all artists seem to share, but peters out when it tries to provide solutions. I think that's because the solutions are all fundamentally very simple and at the same time intensely personal. Pressfield describes all of the frustrations and barriers to creative work as being Resistance. Others call this fear, or procrastination. All the doubting voices and things that stop you starting or help you find something else to do. All the same thing really. His solution is to treat the thing you want to do as a job. You have to turn up, if you want to or not. Day in. Day out. Just get on with it, like you do with your real job. Do the work and the muse will come, the creativity will happen.
So productivity isn't a surrogate for creativity. It is not that we try be productive to be creative. Rather, productivity is a requirement for creativity. You have to be doing the work, putting the time in, for your creative sparks to have a chance to happen. The fickle flashes of brilliance don't come if you aren't vested in the process of making the bad stuff or everyday good stuff along the way to greatness. Turn up. Do the work. Each day. Every day.