If you live in an area with a significant number of wood burners and/or are prone to inversions the problem is real.
Yes, the problem is real because the vast majority or wood burners are burning in smoke dragons, OWBs, open fires, fireplaces, or stoves that are operated improperly and/or with poor wood or poor draft... and NOT burning up to the far-lower emissions potential of newer stoves or low-emission OWBs.
It is not burning wood per se that is the problem, but the WAY that wood is being burned. Think of how much more efficient and cleaner, compared to past decades, that cars, power plants, factories and furnaces are now burning. Rather than being banned outright, it was realized that with respect to particulates all these modes of combustion could be far cleaner.
Wood stoves have likewise come a long way, but the low-particulate potential of newer woodburning technology is not even close to being realized.