The fact of the matter is, game genres by their very nature become established because games borrow mechanics, structural elements, and conventions from earlier games. To have a videogame genre is to recognise a recurrent pattern of plagiarism that draws upon the successes of earlier games as its bedrock. This is a good thing for players: few but the most grizzled gamer hobbyists can face learning entirely original game rules every time they play, most prefer to play something that (in broad strokes, at least) strongly resembles an earlier game they have enjoyed. It means they have less to learn, and it increases the chance that they will enjoy the later game.