We have about 1500 Workbooks and counting on the Tableau server and is there any way we can automate the population of tags in those workbooks without having to reach individual users and asking them to republish the WB? Any leads?

You can probably use the Tableau Server REST API. See the "Batch Add Tags" section: https://help.tableau.com/current/api/rest_api/en-us/REST/rest_api_ref.htm