Works after reading the instructions

It didn’t work first and didn’t throw an error message. Reading the instructions again that come with the plugins’ readme I added

define('WP_LOAD_IMPORTERS', true);

to my wp-config.php and it worked like a charm. Make sure to add

define('WORDPRESS_IMPORTER_EXTENDED_FETCH_ATTACHMENTS', true);

if you’d like to import attachments as well.