Yeah but that's why these people are professionals. Of course it's complicated to do this but statisticians do it all the time. If there's a known confounding factor (e.g. young people don't answer calls) then it can be adjusted for. I know polling isn't perfect but I find these points are less "I have a technical point about the problems with extrapolation/interpolation" and more "This poll doesn't show what I want so there must be a problem"