This is by no means a new problem, but every time I hear about it, it is only an issue in board games sold on Amazon, eBay, and other sites that sell on behalf of third party sellers. I have never heard of anyone getting a knock off game from a reputable board game store (online or brick-and-mortar). Those stores buy games from publishers, either directly or via a distributor (and I fear the day that distributors start dealing in knock-offs).
At this point, many hobbyists know what stores to buy from, but people who are not glued to hobby discussions do not. Unfortunately, I am not sure what publishers or customers can do about it except ask for politicians to hold Amazon accountable for trafficking fake goods.