"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.

I agree with the second sentence but I don't see how it implies the first. "Leave no trace" is a principle of outdoor recreation, not the fundamental meaning of life, and generating greenhouse gases is often necessary to produce goods and services people enjoy.

Agreed. Carbon offsetting always reminds me of this old The Register article: https://www.theregister.com/2008/02/01/bofh_episode_4/