On Wordpress, user-generated content is supposed to go into
/wp-content while other file names and directories (content inside
/wp-includes) are mostly static and predictable as they belong to the Wordpress core.
Directory listing inside
/wp-content can help you enumerate uploaded media files (
/uploads), themes (
/themes) and most importantly plugins (
/plugins). Being able to list all installed plugins without tedious guessing helps to quickly identify outdated versions - which is a great advantage since vulnerable plugins are one of the most common entry points. I've also seen some plugins use their own caching mechanisms and store potentially sensitive data in files with randomized names. A
/tmp directory inside
/wp-content is common, too.
While that's not limited to Wordpress, you might also stumble upon database backups or legacy files with changed names (e.g.
wp-config.php_old) that you wouldn't discover by brute forcing paths. To identify all user-generated files I'd suggest you simply spider the index and diff the directory structure against a default installation.
But although directory listing on Wordpress facilitates information gathering, it usually doesn't pose an immediate, exploitable threat.