Help with simple player movement

Okay, so I have a script here that allows the player to move a game object around the world with their finger. My only problem is, if I were to use this same exact script on a 3d game object, the game object does not move at all. Why is that? Also, touchPos.x and touchPos.y is always a constant number no matter where my finger is placed on the screen. How do I go about fixing this script?

 private float deltaX, deltaY;
 private Rigidbody2D rb;


 // Start is called before the first frame update
 void Start()
 {
     rb = GetComponent<Rigidbody2D>();
 }

 // Update is called once per frame
 void Update()
 {
     if(Input.touchCount > 0)
     {
         Touch touch = Input.GetTouch(0);

         Vector2 touchPos = Camera.main.ScreenToWorldPoint(touch.position);
       
         switch (touch.phase)
         {
             case TouchPhase.Began:
                 deltaX = touchPos.x - transform.position.x;
                 deltaY = touchPos.y - transform.position.y;
                 break;

             case TouchPhase.Moved:
                 rb.MovePosition(new Vector2(touchPos.x - deltaX, touchPos.y - deltaY));
                 break;

             case TouchPhase.Ended:
                 rb.velocity = Vector2.zero;
                 break;
         }

     }
 }