But not all problems at a casino will be found unless the gambler has gambled at that casino, so gamblers will review the casino they choose to gamble at and they generally don't know the problems at all casinos unless they check in detail at each casino to ensure the casino system is fair and does not complicate the withdrawal process.
A wise person is the one who learn from other people's experiences and mistakes. So, if many users say that they had a bad experience with a certain casino or that it is a scam (they need to be trusted users or if they present undeniable proofs) then you don't have to test the casino yourself and repeat their mistake.
In case you did a research and didn't find any review you can trust and you don't have any other option but to try the casino yourself, then at least do it with a small amount of money.
This is the summary of it all, "the experience of others". We have seen many casinos being accused of wrong doings with concrete evidence which the casinos are unable to defend. I don't want to mention names but the evidence are enormous ranging from demanding KYC after winning even when they did not state this in their terms of service, refusal to pay big winnings, closing the account of users without clear explanation of the reason for such action and many other actions that put the integrity of the casino under suspicion. Reports of these incidence are available in various sections of the forum. When you see these issues happening and the casino failed to resolve them convincingly, then it is a sign that something is wrong with the casino.