I know that I can ignore CHANGES on a certain tag, but that still requires me to specify the tag in the tags section of a resource so that TF doesn’t delete the tag. It is a very common practice that other systems outside of TerraForm need to tag resources in AWS that the TerraForm template author does not care about. Therefore, TerraForm needs a way to specify some global option (maybe in the provider definition of the TF template) to ignore a certain set of tags, both the value of the tag as well as the tag key itself.
It looks like the AWS version 2.60.0 has solved this problem almost exactly as I imagined it would work. The AWS provider now has an ignore_tags feature that can ignore specific tag keys and/or tag prefixes globally. Perfect!