Thank you for the clarification. I agree users and the ecosystem overall would benefit from a homogeneous look and UX. However, there is no way to force parachains/dApps to use a your Design Library.
Have you considered talking to them? Is the assumption / expectation that parachains / dapps will just use the Design Library provided?
One issue is, that several parachains and dApps operate on more than one chain. For instance moonwell is deployed on Moonbeam and Base. And Moonwell should look the same no matter on which chain customers are.