A lot of stories are set in worlds that are like reality unless noted. These are settings in which the geopolitical situation is virtually identical to the modern world (minus the presence of a few small isolated nations like Wakanda or Atlantis or hidden supernatural groups like a vampire Masquerade), societal standards are virtually identical to the modern world, history is more or less the same as in the modern world (with the exception of occasional supernatural influence that is often handwaved away so that for most humans there is no functional difference), the geography and ecosystem is more or less identical to the modern world, etc.
- Stories about the appearance of a novel supernatural phenomenon (i.e., zombie plague, alien invasion) in the present day
- Urban fantasy settings, especially those that involve some sort of masquerade that keeps the supernatural hidden and therefore not overtly influencing human history or behavior
- "Superhero" settings like the Marvel and DC universes, which are often more or less identical to present-day Earth in most respects beyond the presence of superhumans (i.e., the presence of Captain America or Namor has caused virtually no differences between the histories of our world and the Marvel Universe, compare with something like Watchmen)
These settings are explicitly not set in an alternate timeline, not set in a fantasy world, and not set in the far future or cyberpunk situation. For these kinds of questions, the context of the present day is essential for answering the question. A question of "how would society react to an alien invasion" or "how would society react to magic" is heavily dependent on present-day infrastructure, societal norms, governmental structure, distribution of resources and technology, etc. The answer would be very different for a world where the Roman Empire never fell, or the year 2500, or a fantasy world with completely different society and government from our own.
As a result, it seems as though it would be useful to establish a tag for those questions which are more or less set in the context of the present day. I had debated making one, having noticed there didn't seem to be a dedicated tag, but it wasn't clear if a tag already existed. We already have a urban-fantasy tag and a modern-world tag, but the scope of these tags and how they do and do not overlap is not really clear. For example, would an alien invasion or superhero question fall under "urban fantasy". The tag descriptions are also incredibly vague.
Overall, we need a dedicated tag for those questions set in the "real world" or something like it to group these kinds of questions together. I am not sure what it should be, or if the urban-fantasy and modern-world tags should be merged. Hence bringing up the issue here.
EDIT: Looking at some of the responses, what it looks like is not that we need a new tag for this kind of question, but rather that we need to consolidate the tags we have, adjust tag descriptions, and use the tags more widely to make them more widely known.