Star ratings show how much the customer likes or dislikes a design.
These ratings are subjective. A star rating doesn’t reflect your design skill — it indicates the personal preferences of the customer.
A low rating means that the design isn’t quite what the customer’s looking for.
If you want more information on the reasons for a rating, talk with the customer about their rating in the comments. This can help you to understand what they’re after, and hopefully improve the rating on your next design.