a basic mistake, like one that a person with no experience of an activity would make

Although he's an experienced movie director, he made the rookie mistake of trying to cram too much material into a mere 100 minutes. 他虽然是一位经验丰富的电影导演，却犯了一个菜鸟级的错误，在短短的100分钟里塞进了太多材料。