The interview process is professional and is focused on managing the process as smoothly as possible.
The negative aspect comes from the decline. This was a non personal chain email, which after 4 interviews should be a phone call, or at least a personalized email. Also delivering an email on a Saturday afternoon is not proper recruiting operations.
Bad experience due only from the decline delivery, Wayfair has a considerable amount to learn in the recruiting process and how declines are handled.