What am I doing wrong with my AI?

I'm trying to make an EnemyAI for a spider that makes the Enemy follow the player regardless of sight, and can climb over objects and terrain to get to the player (I don't have the climbing portion yet) so I'm using transform.position to move the Enemy, but he passes through all objects and terrain except for the ground. What am I doing wrong, here's my AI code.

 using UnityEngine;
 using System.Collections;
 
 public class EnemyAI : MonoBehaviour
 {
     public Transform target;
     public int moveSpeed;
     public int rotationSpeed;
     public int maxdistance;
     private float EnemyGravity;
     
 
     public Animator anim;
 
     private Transform myTransform;
 
     void Awake()
     {
         myTransform = transform;
     }
 
 
     void Start()
     {
         EnemyGravity = 0;
         anim = GetComponent<Animator>();
         GameObject go = GameObject.FindGameObjectWithTag("Player");
 
         target = go.transform;
 
         maxdistance = 2;
     }
 
 
     void Update()
     {
         Debug.DrawLine(target.position, myTransform.position, Color.red);
         Debug.Log(CollisionFlags.Below);
         gravCheck(1);
         Rigidbody rb = GetComponent<Rigidbody>();
 
         myTransform.rotation = Quaternion.Slerp(myTransform.rotation, Quaternion.LookRotation(target.position - myTransform.position), rotationSpeed * Time.deltaTime);
 
         if (Vector3.Distance(target.position, myTransform.position) > maxdistance)
         {
             //Move towards target
             anim.Play("walk");
             rb.velocity = (myTransform.forward * moveSpeed) + (myTransform.up * EnemyGravity);
         }
     }
     private void gravCheck(float gravity)
     {
         Rigidbody rb = GetComponent<Rigidbody>();
         RaycastHit hit;
         if (!Physics.Raycast(transform.position, Vector3.down, out hit, 1.5f))
         {
             EnemyGravity -= 0.7f;
 
             if (EnemyGravity < -15)
                 EnemyGravity += 0.7f;
         }
 
         if (Physics.Raycast(transform.position, Vector3.down, out hit, 1.5f))
         {
             EnemyGravity = 0;
         }
 
         Vector3 move = new Vector3(0, EnemyGravity, 0);
 
         rb.velocity = move;
 
 
     }
 }