"Buying grants to pollute" is literally how cap-and-trade systems work, and they've been extremely effective at reducing pollution. We don't hear about "acid rain" anymore because of cap-and-trade of sulfur dioxide.
But we don't really have cap-and-trade for carbon, so the next best thing is public pressure to be net-zero rather than literally zero.
But we don't really have cap-and-trade for carbon, so the next best thing is public pressure to be net-zero rather than literally zero.