The "average review site" is a rather wide net to cast, you'll find a lot of them are setup purely as affiliate marketing tools - benefiting the owner by using carefully placed referral links. It's in the owners interest to minimize the amount of bad reviews, because they get paid when people sign up and start spending money.
But it also means that it could contain some rather good reviews no? It's actually quite obvious at times which reviews are paid and which are not, it just takes a bit of time and effort to actually filter them out. Well in the end, I'd actually think the experience would be the best review of a casino. Others experience, even if they weren't paid, wouldn't necessarily be the same type of experience one would actually experience themselves.
KYC is also important for casinos and providers. Some key vendors tend to avoid providing games in countries that are restricted somehow. For instance, you can't play NetEnt's games in Australia. You can't access those games if you are trying to play them directly from Australia. You can do it if you use VPN or something, and this is for this case they use additional KYC.
Well isn't that because of the license they use? It's rather normal really. And how does KYC even connect here anyway? Casinos being restricted doesn't necessarily mean that they require KYC, it just means that country doesn't allow users from accessing the site, hence why VPN works.