Why do you need Email Template Builder?  To increase productivity and ensure consistent messaging.   To send emails that include field data from Salesforce records.  We

Salesforce CMS provides a central place to manage content. Assign roles to contributors to decide who sees and does what. Distribute your content across channels such as B2C Commerce, B2B Commerce, Marketing Cloud, Heroku, or Lightning Experience apps. Experience Builder sites can use the Salesforce CMS app to distribute their content while Salesforce Tabs + Visualforce sites can share content through the Connect REST API.