Gambling addiction can be worse if it can't be controlled. Otherwise people may involve with illegal activities to manage gambling fund while they out money and so on. It don't be so easy you told. It needs time to get solved. Blocking websites from browse setting won't help anyone stop from gambling, when they highly feel addiction. Rather first they need to lower the amount during bet and need to keep low money on gambling websites. Thus they can lower the staking slowly and focus/create main source of income. And start using 5-10% of their extra money and make it for entertainment, not for main source of earning. If they have main source, then no need to addict with gambling for money but they can gambler for entertainment and Fun IMHO
I don't really understand what you're saying, one of the reasons and causes they can get into addiction is because they can't control themselves in their gambling involvement, so I think it might be too late to suggest some restrictions to them although basically it's good but as we know that some suggestions most likely won't have much effect if the person is already in the addiction phase because they have the wrong mindset.
I think it's quite difficult to stop them if they are already in the addiction phase because it's quite late, and also yes some other actions might not be very useful like you said by blocking the browsing settings for some sites, everything will be useless if their mindset remains wrong by always holding a lot of hope in gambling. So what is more likely to be able to change them in my opinion is that they are just waiting for time, because usually they will be able to realize if they have experienced a downturn that really traumatizes them, I think that is more likely.