Shader shadow anti-aliasing problem

If i write a shader code for a sprite as below, the edges of the shadow appear as dots. Setting the Shadow option of Directional Light and QualitySettings does not show any change. I think there is a problem with the shader code, what should I do? To briefly describe the code below, i put shadows in the sprite, turn off lighting to prevent lighting from affecting the color, and display the color with Emission.

 Shader "Custom/Sprites/Shadow"
 {
     Properties
     {
         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
         _Color ("Color", Color) = (1,1,1,1)
         _Cutoff ("Shadow alpha cutoff", Range(0, 1)) = 0.5
     }
 
     SubShader
     {
         Tags
         { 
             "Queue"                = "Transparent" 
             "RenderType"        = "Transparent" 
             "IgnoreProjector"    = "True" 
             "PreviewType"        = "Plane"
             "CanUseSpriteAtlas"    = "True"
         }
 
         Cull Off
         Lighting Off
         ZWrite Off
         Blend One OneMinusSrcAlpha
 
         CGPROGRAM
         #pragma vertex vert
         #pragma surface surf Lambert alpha addshadow
 
         sampler2D _MainTex;
         fixed4 _Color;
 
         struct Input
         {
             float2 uv_MainTex;
             fixed4 color;
         };
         
         void vert (inout appdata_full v, out Input o)
         {
             UNITY_INITIALIZE_OUTPUT(Input, o);
             o.color = _Color;
         }
 
         void surf (Input IN, inout SurfaceOutput o)
         {
             fixed4 c    = tex2D (_MainTex, IN.uv_MainTex) * IN.color;
             o.Emission    = c.rgb;
             o.Alpha        = c.a;
         }
         ENDCG
     }
 
     Fallback "Transparent/Cutout/VertexLit"
 }