I do not believe process improvement is bad for innovation. Bad process changes can be bad for innovation. But if we are looking at a research and development organization where the output is new products then process improvement would be focused on improving the processes to make that happen. The type of process improvement would be different than those made to manufacturing a product better.

Some six sigma efforts are little more than cost cutting efforts. And they then might claim a "process improvement" that is really just cutting costs in R&D. But we should confused bad management with the good strategy of process improvement. Here is a good example: Fast Cycle Change in Knowledge-Based Organizations by Ian Hau and Ford Calhoun