Removing All Tags Added by the App
If you're looking to remove all the tags added by Auto Tags app, there's no way to achieve that through the app right now. The app doesn't offer "revert" functionality.
Having said that, you can use "Shopify bulk Remove tags" action or create another workflow in the Auto Tags app to remove the tags, but in both cases, you'll have to manually enter the list of tags that you want to remove.
In order to bulk remove tags, you can use "Shopify bulk Remove Tags" action. Please follow the instructions mentioned on https://community.shopify.com/c/Shopify-Discussions/Removing-tags-from-view-all-tags-list/m-p/468577/highlight/true#M125624 to use this feature.
Using "Shopify bulk Remove Tags" will be much faster than using the Auto Tags app to bulk remove tags from all products as it won't be restricted by Shopify API rate limit.