Your first sentences proved my point, you had to use the word "action" which is in fact a genre. Portal is an FPS, which should tell you that it's a style and not a genre. Plus you mentioned lack of customization, but not all RPGs have customization. Think FF7 or God of War or Zelda, or Shadows of Mordor, where you are all EXACTLY the same character, but they all are "action RPGs"