Sure, no single thing is 100% effective, but that was never the claim for a mask, any mask. But wearing masks, distancing, washing hands, vaccinations, etc, all together, is a lot better than doing nothing.
I agree, a lot of people do not seem to understand that these measures were a "defense in depth" thing.
And also the basic ideas of probability – it isn't _guaranteed_ to protect you, but if it reduces the average rate of infection by x% that's a _huge_ difference at the population level!
I guess that had to be expected given how people flaunted their ignorance of basic calculus curriculum around in the past. Turns out uneducated citizens lead to suboptimal decisionmaking.
A surprising number of politicians are unable to grasp the basic ideas of the exponential function (i.e. it grows _exponentially_).