I think it sounds a lot like an antisemitic slur, so I’d recommend avoiding it in general conversation.
I know linguistic evolution can be confusing and tricky, especially when it involves terms that are or have recently been widely considered derogatory.
Here’s a handy guide for the current cultural moment, to the best of my ability:
“Jew” as a noun, as in “the Jews”, “a Jew”, “that Jew”, etc., used to be (like, mid-20th century) widely considered a bit antisemitic-sounding, mostly because so many antisemites couldn’t stop talking about why they didn’t like “the Jews”.
Jewish people could still acceptably use the term for themselves, though. And as more Jewish people began discussing Judaism and Jewishness and world Jewry in public discourse, use of the word “Jew” as a noun became more acceptable even for non-Jewish speakers.
It’s still more reliably inoffensive for a non-Jewish speaker to say “a Jewish person” rather than “a Jew”, though.
And it definitely sounds offensively antisemitic for anybody to use “Jew” as an adjective. A Jewish person doing so, as in GreysonCarlisle’s example of calling his payot or sidelocks “Jew curls”, is on a par with Black people using the N-word for themselves. In-group users can get away with it but will still sound a little shocking to out-groupers, while out-groupers should avoid such usage like the plague.
Similarly, “queer” used to be considered invariably offensive as both adjective and noun, but is being reclaimed via its usage by in-group speakers, as puzzlegal explained.
But the reclamation trajectory is a little different in this case: “queer” as an adjective has moved farther along the path to general acceptability than “queer” as a noun.
Eh, you’re kind of missing the point. The issue is not “people deciding” that there’s something wrong with turning adjectives into nouns in general. The issue is the existence of a real and significant linguistic history in which the use of certain words, sometimes only in certain contexts, has been genuinely interpreted by most language users as insulting.
You can’t nitpick language use in an artificial vacuum where you just ignore actual linguistic history to suit your rhetorical purposes. Sure, it doesn’t seem to make theoretical sense that it’s offensive to use “Jew” as an adjective but not as a noun while it’s offensive to use “queer” as a noun but not as an adjective. It doesn’t seem to make theoretical sense that we drive on the parkway and park in the driveway, either.
Sensible people understand that meaningful analysis of language use is not just about what seems to make theoretical sense when considered in an artificial vacuum ignoring actual linguistic history.