"Work" is a nonsense term. It's so vague you could give any answer and be right. Do hammers work? Oh, you said yes? Well I meant as a spray on adhesive. Hammers don't work at all when you use them for that.

Yes, they do love their weaselwords. Safe and effective! What is the definition? By what standard are they 'safe'? Or 'effective'? Like Sowell said, everything is a success by sufficiently low standards, and a failure by sufficiently high standards.

Do masks stop disgusting people from sneezing directly into the air? Yes, of course. Does this make them less likely to spread disease? Almost certainly. Is this effect strong enough to have a real impact at the population level? Doesn't look like it, but maybe. Will wearing a mask protect you from COVID? Barely, if at all. Does a non-sick person wearing a mask do anything at all? No.

Excellent response, because you've obviously thought about the matter, and are not spreading mindless BS because you don't want to wear masks. I think this is unfortunately different from the vast majority of people, who either follow supposed authorities, or who just come to conclusions based on prejudices.