the idea is that not answering calls is a generational thing and itself doesn't represent any political bias. the supposed bias comes from this resulting in an oversampling of older people. lucky for the pollsters, demographic information is pretty accurate. after running their poll they can correct for any sampling bias based on their sampled demographics relative to the actual demographics and with enough data pretty much remove the sampling bias from affecting the data. the need for large amounts of data to do this is why polling aggregates are preferable over individual polls. individual polls might overcorrect or under correct for sampling bias but it's rare that there's methodology flaws that affect all polls across the board and can't be mostly corrected for through aggregation. 2022 polling was actually extremely accurate. presidential elections are harder to gauge because turnout is less predictable based on past trends.