The documentation in Shoreditch states:
- Drupal 7
- CiviCRM, v5.0+ recommended
- "CiviCRM Theme" module enabled
- "Seven" theme set as CiviCRM Administration theme
My understanding is that the layout part is then heavily depending on the Seven theme, which is why it appears so differently in WordPress. Please correct if this is a misunderstanding.
Try this extension from bgm: https://civicrm.org/extensions/shoreditch-wordpress-workarounds
It's working better than the CiviCRM Admin Utilities WP-Plugin.