it's descriptive, carries a lot of connotation, none of which actually involves the city or the people of shanghai, I don't get why anyone has beef with it.
(Since I'm getting downvoted anyway - anyone avoiding the overwhelmingly more common near-synonym, "drafted", is doing so because they don't like to remember that the US can still do it, too.)
The former I expect to be a highly managed process through which the state renders you unable to seek employment, housing, education, free movement etc, in order to coerce or capture you violating the law, encouraging you to present yourself willingly rather than dealing with criminal charges in addition to or instead of conscription.
The latter, my expectation is that mercenary recruiters, driven by sales team esque metrics, eventually resort to pulling random young men off the street, out of bars, etc, based on a best guess of the young man's age. It's far more chaotic, error prone, and disruptive to family life, while being less coersive.
Did you know all words are just sounds with an arbitrary connection to what they describe (except the unusual case of onomatopoeia, of course)?
It's exactly as descriptive as most other words, and the benefit over a neologism is the arbitrary connection has already been established in speakers' minds.
I don't think that's what "descriptive" means. The term is as descriptive as much as "laconic" or "china" or "japan" (meaning varnish) - in each case, you can't independently derive the word's meaning from the original place name.