"What's your sign" is the fossil of pick up lines — so dated it has come all the way back around, powered by the astrology revival. Half these lines play it straight for the star-chart crowd; half mock the cliché itself. Know which register your audience wants before opening.
With anyone who has an ascendant memorised, the sincere versions are genuinely effective. With everyone else, the self-aware ones are the safe play.
The astrology revival rescued this line from the seventies and handed it a new audience that genuinely wants to answer. With chart-readers, play it straight and have your own big three ready — the follow-up conversation is the entire point. With sceptics, mock the line while using it; the irony is the flirtation.
Both registers work at parties, and the app bio that lists a sign has pre-consented to the material. The other fossils live with the classic lines, and the astronomy collection serves those who prefer their stars with physics.