A comparison would be the incentives around tax filing. Everyone has the financial incentive to cheat, but the enforcement is good enough (probability of being caught * punishment) that most people don't. The question is: how good is the enforcement mechanism as applied to sellers of carbon credits, and what is the added cost to the taxpayer of setting up such a system.
Carbon capture is real, carbon offsetting isn't. Offsetting is like making a "saving" by not buying something and then immediately spending the money you "saved".