Why do high mountains not prevent the Earth from being considered a spherical body?

The highest mountain – Everest, about 9848 meters, compared to the radius of the Earth, about 6371.032 kilometers – is negligible. The ratio is 1: 646.94. For clarity, let the Earth be the size of a soccer ball, then Everest will have a height of 0.17 millimeters. I think it will not show up in the game.) Still, our planet is not a ball, its shape is defined as a geoid. True, the geoid, due to the complexity of the shape, does not have a wide practical value.