Right-click on the invitation, and (at least in the desktop view of FB – I don’t know what the mobile view looks like) you’ll have an option to “ignore all” either “from this user” or “from this game”. So as each new game is released, it’s a one-time thing to “ignore requests from this game”. I think I’ve only had to deal with one unwanted game request in the past twelve months or so now, which is an acceptable rate of these spurious requests to me.