To quote from the Usage guide for tag site-recommendation (applied ~5 times, once a duplicate):
Don't know where to ask your question on the Stack Exchange Network? Give as much detail as possible about the question you'd like to ask, and the community will help you find the appropriate site.
For the same tag on META: (applied 1,576 times – I assume their statistics are reliable):
After looking through the site list, https://stackexchange.com/sites, you don't know where to ask your question on the Stack Exchange Network? Give as much detail as possible about the question you'd like to ask, and the community will help you find the appropriate site.
Aside: Is one of the above plagiarism?
We already have tag scope (You should always favor existing tags) to cover what is and is not off topic for Web Applications, its Usage guide:
Use this tag when examining what is on-topic or off-topic on this site, and why.
and with a highly slumberous meta are unlikely to provide a fast response, relative to META (who are receiving 7.7k visits per day).
In addition, META is shown as having twice as many users, so presumably a broader representation of the 170 SE communities, so possibly better quality of response.
SO meta has such a tag, but 77 out of the 224 Qs there are Closed.
SU meta has 2 Qs so tagged.
Server Fault meta, Ask Different meta, TSE meta (and maybe others) have no such tag.
If a Q is deemed off topic here it might be a greater service to OP to point to where to ask where to ask than to point directly to another specialist SE site.