OpenStreetMap has been around for almost 20 years and our data is used by a lot of people: researchers or geographers often run various type of queries.
Those tags were certainly introduced for a good reason.  And yes, indeed, there is no requirement that only one object contains the ISO-3166-1 code; the map has functioned fairly well with that, exactly because there is more than a single tag to identify an object.

The best way to discuss this is to start a topic on the community forum (https://community.openstreetmap.org/) explaining why you feel like we should delete all those tags, and see what people say about this idea.