Destroy 2D Objects when in contact

hi, i'm trying to do some exercising by making infinite runner game and currently i'm having trouble when destroying generated obstacle. The problem is that it doesn't destroy the obstacles at all when the obstacle come in contact with the destroyer

This is the script used to destroy obstacles which i obtained from this forum but it still doesn't work

 using UnityEngine;
 using System.Collections;
 
 public class DestroyObstacle : MonoBehaviour
 {
     void OnCollisionEnter2D(Collision2D col)
     {
         if (col.gameObject.tag == "Obstacle")
         {
             Destroy(col.gameObject);
         }
     }
 }

and i also have tagged all the obstacles as "Obstacle" and keep the Is Trigger box unchecked i'll provide the details in the attachment

The prefab named "rock" is a child to a parent prefab called "Obstacle[n]" also tagged Obstacle

i've tried searching all over the place but still can't find the solution, i'm sure i missed something

Thanks in Advance!