InitDB.pl is only able to create a new database from scratch. If something already exists, it will avoid messing it up and leave it in place, thus the error messages. Since you mentioned you are “recreating” the database, it is not surprising that these schemata already exist.
There is a dedicated script for recreating database, which basically DROP everything before calling the regular script, see the section “Recreate database”.
As you already fetched the data dumps with your last attempt to create the database, you can avoid downloading these again by recreating the database as follows:
sudo docker-compose run --rm musicbrainz recreatedb.sh