Online gambling just made gambling easier and more accessible than visiting physical shops, I don't know of oys right to say that it leads to gambling addiction because more people having access to gambling in an easier and flexible fashion does not not amount to gambling addiction. Although it has the tendency of making people gamble beyond limits since the deposit method is easy and smooth but I don't believe it leads to gambling addiction.
I also think that with the increasing ease of access to gambling platforms, it will not actually increase gambling addiction, because it comes back to gamblers how they can manage their gambling habits. Because if the person really can't control themselves, then whether it's online or offline gambling, they will easily become addicted to gambling. The point is, never blame online gambling for making it easier for people to gamble, but blame the gamblers who play and become addicted because of it.
Well what you said is also true, it is true that in the end the problem of addiction really depends on the gambler themselves on how they treat the gambling activity itself regardless of the problem of easy or difficult accessibility, you have said the right reason that even though for example a gambler is involved in a type of physical casino where accessibility is quite difficult but if for example they have the wrong approach then surely they will also be very easy to get addicted, so it can be said that the problem of addiction does not depend on where you gamble but rather depends on how you treat the gambling activity.