You can have people very happy about your product and still little to no "word of mouth" if your product is niche. For a niche product each happy user would ha

You can have people very happy about your product and still little to no "word of mouth" if your product is niche. For a niche product each happy user would have to tell many other potential user to make one conversion. So practically niche products rarely get viral. Hence why Steam focuses on games that can be sold easily, not especially those with the happiest users. To make a game greenlit the voters vote on the screenshots and the beginning of the video, not the gameplay.