The main problem seems to be that these tags are considered too general, that is applying to a large majority of the questions on the site. However, there are some situations in which a similar variant is required to convey meaningful information. For example, in this question, I am looking for articles on development and history of the fantasy-genre. So, tagging it with fantasy does make sense because it looks at fantasy as a whole, but there is a ban on the fantasy tag. I request that we unban the fantasy and sci-fi tags, to be used in questions that talk about the genre as a whole.