> An individual can reduce their contribution to climate change by up to 30% by simply forgoing meat and dairy

So they go from their contribution to climate change being completely insignificant to it being 70% of completely insignificant.

If I dropped all meat and dairy it would reduce the world's annual emissions by 0.0000000026% (if we are optimists [1]).

This level of reduction only matters is a very large number of other people do it too, and getting that to happen requires a lot of top down effort.

[1] Realistically cows are produced in integer amounts. My foregoing burgers and steaks would not reduce the number of cows. At most have a minuscule affect on prices too low to be detected. Same for other meats and dairy.