The problem is that defining a rookie card outside sport involves a variety of cards and card adjacent items from all over the place. Often the earliest card will be a postcard or a promo card. For example, the earliest Marx Brothers card I know of is the vaudeville Exhibit card from 1926.
For recording artists the earliest card is usually a promo item from the label.
Or a studio card for an actor:
That’s all logistics. Where I think it goes too far is RC on a fictional character. Umm, no. They don’t exist.