The exposure triangle is incomplete — it ignores the most important variable: distance to subject

Aperture, shutter speed, and ISO are the exposure triangle. But the fourth variable — distance to your subject — controls depth of field more than aperture alone. At f/2.8, a portrait at 3 feet has razor-thin DOF; the same lens at f/2.8 shooting a landscape has enormous DOF. This is why phone cameras have such deep DOF despite wide apertures — the sensor is small and the focal length is short.