You are failing to understand that the earth spins, on that tilted axis, while the planet rotates around the sun. But the tilt does not rotate to continually face the sun. Imagine that same diagram but with the sun on the right instead of the left. Thats a representation of 6 months after the view in the diagram. But the earth is spinning during all of that. You need to practice your visualization of 3D systems. Its clear you are unable to properly visualize what is taking place that would make your diagram meaningless. And in fact your diagram does less to explain the seasons than the spherical model im describing. The seasons are due to the sun being above or below the equator on average due to the rotation around the sun, combined with the tilt of the earth axis that does not rotate but stays at a fixed angle.