Err I guess I trust the ones that I do KYC with? I've never had issues after all with the ones I've played with. I don't know how the process of KYC goes exactly in these casinos so I can't really recommend a way to improve the accuracy of whatever they do, maybe convene in cases where KYC fails? What are the possible issues when KYC fails anyway?

Casinos require KYC in the first place when big wins happen because they're afraid of money laundering. It isn't wrong to say they target those audiences but at the same time, some context is needed so as to avoid some misunderstandings (I won't deny that there are some casinos that take advantage of this idea though). I guess the least a casino can do so as to avoid issues is if the amount of money involved in an account is more than the amount that they deposited, they can give the initial deposit amount (or whatevers left with it). If not, then they simply don't need to give anything and just lock the account.