我对这个问题的理解是，您希望在2D中从玩家位置向鼠标位置投射一条光线。如果不是这样，那么您应该编辑您的问题，并给予更多关于您到底想要实现什么的上下文。
如果我理解正确的话，那么答案就是你构建了错误的光线。你所做的是从摄像机的Angular 投射光线，你可以认为这是通过你的显示器向游戏世界投射光线。
若要从玩家角色的Angular 获得光线，光线应该从玩家的位置朝向屏幕空间中的鼠标位置。

// get the player position in screen space
var playerScreenSpacePosition = Camera.main.WorldToScreenPoint(playerPosition);

// calculate ray direction (to - from = direction)
var rayDirection = Input.mousePosition - playerScreenSpacePosition;

// if direction vectors length should be ignored then normalize
rayDirection.Normalize();

// construct the ray with the player being the origin
// (if needed could be Ray2D as well by ignoring 'Z' axis, needs converting position and direction to Vector2)
var ray = new Ray(playerPosition, rayDirection);

// cast for a hit
var hit = Physics2D.Raycast(ray.origin, ray.direction, Mathf.Infinity);

// alternatively: if the length of the raycast shall be defined by the directions magnitude
// (only if direction not normalized, otherwise the rays length will always be one)
hit = Physics2D.Raycast(ray.origin, ray.direction, ray.direction.magnitude);