Why is the template blacklisted?

It could be that most users are marking you as SPAM or not intended to receive messages for a specific template. It could also be that template(s) contains content that violates WhatsApp’s Commerce Policy.

Please refer to the link below to know more about blacklisting of a template.

https://developers.facebook.com/docs/whatsapp/message-templates/guidelines#quality-rating-and-template-status