How do move a player on an xz plane with a top down orbit camera?

Hello world,

so in my game I have a 3rd person camera that is looking down upon my player and has the ability to orbit around him/her when holding down the right mouse button. (granted I cant change any of the offsets when in game, another problem to work on)

 public class cameraController : MonoBehaviour {
 
     public float turnSpeed = 4.0f;
     public Transform player;
     public float zOffset = 7.0f;
     public float yOffset = 8.0f;
 
     private Vector3 offset;
 
     void Start() {
 
         offset = new Vector3(player.position.x, player.position.y + yOffset, player.position.z + zOffset);
         transform.position = player.position + offset;
     }
 
     void LateUpdate () {
         if(Input.GetMouseButton(1)) {
             offset = Quaternion.AngleAxis(Input.GetAxis("Mouse X") * turnSpeed, Vector3.up) * offset;
         }
 
         transform.position = player.position + offset;
         transform.LookAt(player.position);
     }
 }
 

Using this camera controller I want to be able to move the player using the WASD keys depending on the camera. This is what I got.

 public class playerController : MonoBehaviour {
 
     public float moveSpeed;
 
     private Rigidbody rb;
     private Camera playerCamera;
     private Vector3 keyboardInput;
     private Vector3 playerDirection;
     private Vector3 moveVelocity;
     private int cameraLayermask;
 
     // Use this for initialization //
     void Start() {
 
         rb = GetComponent<Rigidbody>();
         playerCamera = FindObjectOfType<Camera>();
 
         // Layers for Camera Raycast to focus on //
         int groundLayer = 8;
 
         // Add layers to Layermask
         cameraLayermask = 1 << groundLayer;
     }
 
     // Update is called once per frame //
     void Update() {
 
         keyboardInput = new Vector3(Input.GetAxis("Horizontal"), 0f, Input.GetAxis("Vertical"));
         playerDirection = playerCamera.transform.TransformDirection(keyboardInput);
         playerDirection.y = 0f;
         print(playerDirection);
         moveVelocity = playerDirection * moveSpeed;
 
         if (!Input.GetMouseButton(1)) {
 
             Ray cameraRay = playerCamera.ScreenPointToRay(Input.mousePosition);
             RaycastHit hit;
 
             if (Physics.Raycast(cameraRay, out hit, Mathf.Infinity, cameraLayermask)) {
 
                 Debug.DrawLine(cameraRay.origin, hit.point, Color.blue);
 
                 transform.LookAt(new Vector3(hit.point.x, hit.point.y + 0.5f, hit.point.z));
             }
         }
     }
 
     void FixedUpdate() {
 
         //Replace Gravity
         moveVelocity.y = rb.velocity.y;
         rb.velocity = moveVelocity;
 
     }
 }

Since I'm using

playerCamera.transform.TransformDirection(keyboardInput)

the cube is going to want to get pushed into the ground, in order to prevent this I added

playerDirection.y = 0f

this however has lead to a very slow moving forward motion.

What can I do to fix this?