I think deforestation-based carbon credits are a particularly easy place for scams, or even accidental double-selling, or selling acres that wouldn't have been cut down to begin with.

I think buying credits from GoldStandard [1] is a safer bet. While I'm sure there's some of the same shadiness occasionally, I think that a lot more work goes into vetting projects. The majority of the projects I fund are small solar, wind or hydro plants. While many of these plants might get built anyway, I think the funding from GoldStandard may make the difference for lots of these small projects.

1. https://marketplace.goldstandard.org

Carbon offsets are a financial instrument, which is very different than an approach that treats CO2 as a waste product. By nature trying to solve this via a financial instrument likely won't motivate anyone, it's just a way for organizations to play hot potato and literally pass the buck. However, if we were to treat CO2 emissions as a waste product, it would likely have more restrictive industry regulation around how organizations are required to manage their C02 waste by products.