We can't. My question is how can we resolve it when (not if) it arises.
I think this is a really important question, and one that can be really useful for both designers and gamers looking to buy a new game to think about.
From a designer standpoint, that is making it really clear what your game is, and what it isn't. In the ongoing Masks example, I believe it would have been a good idea to be clearer about this. The best examples I can think of in terms of doing this well are the games
Monster of the Week and
Monster Hearts. If you look at them at a high level, they might seem similar, but they aren't. And I think the designers did a great job of making sure everyone knows that.
Did Masks do that? There is a disagreement. I knew about it, but there are clearly people who weren't on the same page. You will have to ask yourself if that's a reasonable discussion to have. I do think that it's instructive if you're creating a game that is different from other games in what people would think of as a similar genre. As a designer, saying "Hey, you should have known better" is not going to win you any goodwill.
From the perspective of someone
buying a game, you need to do your due diligence. This is easy for us here at EnWorld because of all of the awesome work that everyone does in showcasing new games (hey, if you haven't heard it said recently, I appreciate you!)
Looking into what a game is crucial if you don't expect to have a game sitting on your shelf or in your Dropbox. And there are a ton of resources about that. Of course, me saying that will be useless, as the sort of people who need to hear that aren't coming on EnWorld or similar sites.
I think there's a useful conversation to be had even if you think Masks is a great game and entirely clear in its presentation.