This alternative seems to work:

createbucket:
  image: minio/mc:latest
  networks:
    - main-network
  entrypoint: >
    /bin/sh -c "
    mc alias set s3 http://minio:9000 <name> <password>;
    mc mb --ignore-existing s3/media;
    mc anonymous set download s3/media;
    "
  depends_on:
    - minio

I.e. I used mc alias set instead of mc config host add.