My object is rotating crazily - 2D

Hi, I want my object to simply rotate and look towards where I click (In 2D), but instead it kind of faces my click in 3D, so it rotates around the X and Y axis instead of just Z. I have tried many different types of rotation strategies, but none seem to work the way I want them to. If anyone could help, that would be greatly appreciated. Cheers!

using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI;

public class PlayerShip : MonoBehaviour {

 public Text massText;
 public Text thrustText;

 [Header("Attributes")]

 public float speed = 0f;
 public float mass = 1f;

 [Space(5)]

 public Rigidbody2D rb;

 [Space(5)]

 public float distanceToClick;
 private Vector3 mouseClickPos;

 [Space(5)]

 public float smoothTime;
 private Vector3 velocity = Vector3.zero;

 void Start()
 {       
     rb = GetComponent<Rigidbody2D>();
 }

 // Update is called once per frame
 void Update()
 {
     GameObject placementManager = GameObject.Find("PlacementManager");

     if (placementManager.GetComponent<PlacementScript>().isAnObjectSelected == true)
     {
         transform.rotation = Quaternion.Euler(0, 0, 90);
         transform.position = new Vector2(Mathf.Round(transform.position.x), Mathf.Round(transform.position.y));
     }

     mass = mass / 2;
     rb.mass = mass;
     smoothTime = rb.mass;

     float massRounded = Mathf.Round(mass);
     float thrustRounded = Mathf.Round(speed);

     massText.text = "Mass: " + massRounded;
     thrustText.text = "Thrust: " + thrustRounded;
 }

 private void FixedUpdate()
 {
     GameObject placementManager = GameObject.Find("PlacementManager");

     if (Input.GetMouseButton(1))
     {
         if (placementManager.GetComponent<PlacementScript>().isAnObjectSelected == false)
         {
             mouseClickPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);

             distanceToClick = Vector3.Distance(transform.position, mouseClickPos);
         }
     }

     if (distanceToClick >= 0.5f && speed > 0)
     {
         if (placementManager.GetComponent<PlacementScript>().isAnObjectSelected == false)
         {
             Vector2 dir = mouseClickPos - transform.position;
             var angle = Mathf.Atan2(dir.y, dir.x) * Mathf.Rad2Deg;
             transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);

             transform.position = Vector3.SmoothDamp(transform.position, mouseClickPos, ref velocity, smoothTime);
         }
     }

     transform.position = new Vector3(transform.position.x, transform.position.y, 0);
 }

}