Shoreditch looks different in wordpress
The documentation in Shoreditch states:


  Requirements
  
  
  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.

If you use the CiviCRM Admin Utilites plugin, you can enable WP Admin Styles, published blog post with an overview.