As of SERVER-80372, the router converts any implicit collection creation into an explicit creation. Additionally, the router will become the only entry point for any MongoDB deployment (project represented by SERVER-52468), and we plan to disallow direct shard connections (SERVER-77073). 

This ticket is to explore removing internal support for implicit collection creation. We may also have to realign internal code paths to create collections explicitly. Also, any specialised maintenance role that bypasses SERVER-77073 would have to create collections explicitly; assuming this downstream change is acceptable, we should be able to streamline some of the local catalog logic around collection creation.