I suspect the "seller"¹ told you what they did to entice you to buy the camera. What the seller told you isn't exactly true and correct.
¹ Which, as it turns out, is not a seller of this camera at all. Rather, that person described as the "seller" was advising the existing owner of the camera that the scene modes aren't that important anyway. Possibly to minimize the fact that the "seller's" shop couldn't fix the problem.
In fact, it is pretty much the opposite case: scene modes are a way of the non-professional telling the camera what the conditions of the photo are so that the camera can use the appropriate settings to maximize the chances of a successful photo.
One example: Snow or beach scene.
The professional photographer understands that a camera doesn't know if we are photographing a black cat in a coal mine or a white cat in a blizzard. The professional knows how to alter the camera's settings to make the scene look bright without totally overexposing the image or dark without totally underexposing the image. The amateur does not usually know how to do this.
Unless we tell the camera to do differently, the camera will try and make everything a medium brightness. So if the camera is set on full "Auto", a picture of the snow will look bleak and gray because the camera will expose bright white snow as medium gray!
"Snow/Beach" scene mode to the rescue!
We don't have to know how to adjust exposure for snow or bright sand at the beach, we just have to know to tell the camera we're taking a picture of a very bright scene by turning the mode dial to "Snow" and the programming in the camera will do the rest!
The same is true of the many other scene modes. It gives the amateur a way to tell the camera what kind of scene they are shooting and the camera will attempt to pick the best combination of shutter duration, aperture, and ISO to use for that particular kind of scene. The amateur doesn't really need to know what the camera does to get there. They just need to be able to recognize the difference between a bright sunny day at the beach (Snow/Beach scene mode) and a night out on the town (Night portrait scene mode). They just need to be able to tell the camera they are shooting a running subject (Sports scene mode) or a static nature scene (Landscape scene mode). This allows the camera to emphasize what is most important for a particular type of shot. If conditions are less than ideal, the camera will use one of the other, less important factors for a particular type of photo to compromise and keep the most important thing as optimal as possible.