I agree, but prevention would require collective effort. Everyone can of course make sure for themselves that they neither feed these casinos money with deposits nor data for KYC, but more often than not, these casinos are still successfully fishing for either newbies or gamblers who can't resist seemingly great bonuses.
You are right that individuals being cautious won't save the market. The problem is not the free-rider effect, it's that gambling sites don't run short of targets because there's a constant influx of new victims.
People join gambling communities in droves every month without realizing what kind of trap they are jumping into. That is why warning posts won't help, people need to be warned before they make their first deposit.
The neverending influx of new potential victims is one great incentive for scam casinos to keep going, but you have probably noticed how many casinos look the same, right? The technical requirements to quickly set up a casino that functions well, looks serious and gets promoted within no time are far too low. In the past, setting up a casino took some effort, but I think it doesn't really require much these days. If you want to run a serious one, yes, you need huge amounts of liquidity, but if you want to run a scammy money grab, it is pretty quickly done and once you have done it with one casino, you can just buy new domains, change the layout or colours slightly and go again as often as you want.
Think about it, if these stupid emails work where some guy says you should send $1,000 to then receive $100,000 in return, copying casinos all day long will work just as good.
There are several casinos that let you play without KYC, why bother handing over your sensitive data in the first place...
That is the best point, really. Non-KYC casinos pretty much have already fixed this issue. If you are going to be okay with a shady unregulated casino, might as well use one that does not require you to provide any information at all? Those are better than ones that do.
I still believe gamblers are hopping from casino to casino because of bonus offerings. It is surprising because most of the time the wagering requirements are unrealistic, but you can be absolutely sure that once somebody luckily fulfills those wagering requirements, the account will get shut down if it isn't a casino with a big name in the industry. Even then you are are not safe.