It depends on the hook of the game. A game like Journey would utterly fail without the aesthetic that it has, because the point of that game IS the aesthetic and not the pure mechanics of the gameplay. On the other end of the spectrum, a game like chess or minesweeper needs absolutely no graphical representation at ALL to be played or enjoyed.

A lot of modern games are trying to bridge the gap between cinema and gaming and I think graphics are important for cinematic narratives to be taken seriously. Not necessarily just the technical wonder of the graphics but how well they accomplish their own aesthetic (can you imagine Shadow of the Colossus or Okami without the graphic stylings that those games have? Mediocre.)

Saying something like "graphics aren't important" is a pretty thoughtless blanket statement imo and I'm not sure what there is to argue. Whether they are important or not depends on what type of game is being made. Graphics absolutely could make or break a game depending on what a game is trying to accomplish.