The problem with waveguides are the manufacturing defects are on the micron level, and you need to get those channels perfect - then produce the same pattern a

The problem with waveguides are the manufacturing defects are on the micron level, and you need to get those channels perfect - then produce the same pattern a few more times for other colors, and hope they all perfectly line up. I don’t see 3D printing being a solution here for a very very long time