The site currently has a childrens-literature tag. I'm not quite sure what its purpose is.
Do we need this tag, and what should it be used for?
Tagging should be simple. Whether the Just William stories should be classified under children's literature is a fascinating and multifaceted question for the main site. But we shouldn't have to get into complex literary debates to decide whether questions about Just William or Harry Potter or whatever have you should be tagged with a tag like childrens-literature. Tagging should be simple, genre tags are anything but.
There's also the fact that we already have a lot of tags. Questions are tagged with title tags, author tags, and language tags. Adding a genre tag puts us perilously close to the five tag limit. If we add genre tags, we should remove title tags.
If there's a question about the Science Fiction genre, or about the Children's Literature genre, then they should be tagged with genre, not science-fiction or childrens-literature. The reason for this is simple. Consider the question "Should the Wheel of Time series be classified as Science Fiction or Fantasy?" If we had a science-fiction and a fantasy tag, the logical decision would be to tag that question with both tags. Since the question would presumably have an author and title tag as well, we would be approaching four tags. Which isn't that bad for that question, but I could imagine questions that compare three or four different genres causing problems. Using just a genre tag seems a lot simpler.
But what if someone has a question about a genre, not about a book in a genre or classifying a book into a genre... What if I wanted to know about a trope within a certain genre? Does it still make sense to use the generic "genre" tag?
I gave a practical reason in part 2. Here's the equally practical but more literary reason.
The reasoning underlying all of my objections to genre-based tags is the understanding that genres are not clearly defined, objective categories. Exactly like the concept of literature, the concept of genre is marketing and politics. Some interesting examples of the way marketing and politics create genre:
The genre of solarpunk was created before there were any stories to label as solarpunk (thank you BESW for telling me about Solarpunk). Which was the point: creating the genre of solarpunk, and writing the equivalent of a mission statement describing why solarpunk was necessary, inspired people to start creating solarpunk books.
Harry Potter was originally marketed as children's literature. That changed in part because adults also enjoyed reading Harry Potter, and the adults didn't like having something they enjoyed being labeled as for children.
Genre is fluid. Genre is constantly making exceptions to any definition you give it. Genre is the exact opposite of what a tag is supposed to be--an easily definable concept.
I'm not sure how a question about a trope should be tagged. First of all, I'm not even sure if we should encourage questions about tropes; it might not be the best concept for studying literature. But I do know that individual genres are not objectively definable, and therefore I would question the notion that a genre can be objectively associated with a trope.
To be fair, I don't really have a clear definition of what a "genre" is. But it seems odd to me to have a genre defined purely in terms of the target audience, rather than in terms of what the stories are actually about.
We don't necessarily need to agree on an exact definition of genre. But when we see a category of books defined by marketing and politics, that's a good sign that we're talking about genre.
If I had to give a specific definition of genre, I would give a definition along the lines of the one BESW gave in a comment to this answer:
Functionally speaking, genre is usually shorthand for "people who like X will also like Y." It's most often applied by marketers and distributors, rather than authors or analysts, in order to funnel likely audiences toward the work. Genre labels also are not exclusive; you can (and should) have a decopunk pulp SF alt-history space opera mystery.
Per Stack Exchange policy, the rules for tag burniation are:
That being the case, I think that burniation would be appropriate here.
I suppose other questions we could ask are: