Where I agree with you is that _policy_ is a much more direct and effective method of achieving similar ends. However I don't think eating less meat is comparable to carbon credits. The IPCC specifically lists it as a tried and true strategy for reducing greenhouse emissions.

The substitution of meat for other protein sources has real (albeit lagging) effects on the agricultural economy. Less people buying meat leads to less production of meat at scale, which in turn results in reduced deforestation (and potentially reforestation). Producing less meat leads to less greenhouse gas production at several points in the chain, most notably from reduced number of animals, but also during production and logistics. More forests contribute to carbon capture and biodiversity.

Probably the two biggest obstacles to consumer based solutions have been policy that subsidizes the cost of meat, and the cultural backlash to the idea of eating less meat (despite the many health + environmental incentives to reducing meat consumption overall).