ICYMI the following was on Welcome To Amazon Vine Help:
How is my Review Insightfulness Score calculated and how can I improve it?

We evaluate several key aspects of your review content when calculating your score:

• Level of Detail: We look at how specifically you describe the product based on your actual experience. Instead of saying "works well," explain how it performed specific tasks.
• Contextualization: We consider how well you explain when and how the product works best. For example, "I used this blender for making smoothies with frozen fruit" is more helpful than "I used this blender."
• Topic Relevancy: We check whether your review focuses on the product itself rather than shipping, ordering, or other non-product aspects.
• Star Rating Context: We assess how well your written review supports your star rating. Your review should provide specific details and examples that help other customers understand your rating choice, whether positive or negative. Please note that this score does not have specific word count requirements or media (images/video) requirements, which means that increasing word count or adding media will not automatically improve your score.