There is absolutely nothing weird about a reputable casino failing to complete a user's kyc verification request, the reason for the failure will usually be attached to what ever email or message they sent to the user.
For the several reputable online casinos I personally have used, they usually don't surprise their users except those that want to be surprised, that is, if you read their documents on withdrawals, they usually explain how accounts with certain level of verifications are limited to certain amount of withdrawals every 24 hours, week or month, and if you are in a low level kyc rank and are going to withdraw funds that is above the limit for that rank, you will be forced to submit documents that is required for the next level of their account verification levels, failure to submit the requested document is what usually lead to the casino's failure to verify the user and process his or her withdrawal.
The reputable casino's KYC procedure is very clear and easy. If you submit the correct documents for the KYC, there is every chance that your KYC will be approved. Casinos want customers and they will never want to deny the legit KYCs and restrict people from not gambling.
The problem only comes with those casinos who want to scam and do not let people withdraw and make excuses for fake KYC etc. Such casinos are either new ones whom reputation are unkown or they could be old ones too that are known for their scams. That is the reason why i avoid such casinos and gamble only at reputable ones even if i have to do a greater level of KYC, its ok to have a piece of mind.

You are right bud, absolutely correct. And this is also the reason why it is always adviced that gamblers don't go depositing high or big amount of money on casinos that are new, the tendency for them to see such an amount of money and want to cheat the gambler out of the money will always be there, specially if the casino is one that is managed by people that are not financially buoyant.
And concerning old and once trusted casinos also engaging themselve in such act as trying to use kyc to cheat their users off their hard earned money, "nothing lasts forever" should be very common phrase for many of us, and to avoid being a victim to such, or to avoid losing all your money to such casino, it is also adviced that we should never leave on our casino accounts; amount of money that we can not afford to lose, because in the end, change is still the number one thing that is constant, which means that even a well trusted casino today can turn it go rogue tomorrow.