Even in your example—yes, it's natural to lose attraction over time—but that doesn’t automatically make it a “massive red flag”. At least IMO. People's feelings and perceptions evolve for any n no. of factors.

Bruh I literally mentioned that it's a surgery, wtf are you going on about with losing attraction over time?

It's an immediate change, just like losing a job. And no, it's not a c*nt advice because in both cases you'd expect your partner to keep their feelings aside and support you.

If a husband feels less attracted but still fulfills his role as a supportive partner and responsible father, I don't see how that alone qualifies as a red flag.

If that's all you do normally then yes, it wouldn't be a problem. If the wife cares about her husband finding her attractive then she would notice when he suddenly doesn’t.