A number of individual users, and institutions in the Canvas Community, are calling for Canvas to streamline the processes for adding Rubrics to assignments that are using the Turnitin LTI external tool.
 
While there are some workarounds for adding Rubrics to Turnitin LTI assignments, the current workflow for adding Rubrics does warrant some simplification.  
 
Read more on Canvas Community and vote for a simpler method for adding Rubrics to Turnitin assignments:
Request assistance for workarounds to add Rubrics to Turnitin LTI assignments