Feather shuttles are significantly superior when it comes to playability. If they had to hit shuttles in the dark, all the top players could identify a feather shuttle just from the feeling of hitting it. Its a cleaner hit, it gives more feedback, which in turn allows for more consistent higher quality shots.
As long as that is true, no one at bwf will push for synthetic at the top level. With science and engineering, you are limited by the attributes of the materials you have, and what you can do with it. It’s not always ‘where there is a will, there is a way’. Anyone who finds a way to make synthetic shuttles that are indistinguishable from feather, could undercut the market and make millions. I won’t say it’s impossible, but it’s out of reach for the time being.