Performance issue: Camera.Renderer - Drawing - ... - Clear needs 50% CPU ???

Following shader is for UI ... Apply it to each and every UI element and let me know if you've got any better results

 Shader "Custom/UI/Fast-Default"
 {
     Properties
     {
         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
         _Color ("Tint", Color) = (1,1,1,1)
     }
 
     SubShader
     {
         Tags
         { 
             "Queue"="Transparent" 
             "IgnoreProjector"="True" 
             "RenderType"="Transparent" 
             "PreviewType"="Plane"
             "CanUseSpriteAtlas"="True"
         }
 
         Cull Off
         Lighting Off
         ZWrite Off
         ZTest [unity_GUIZTestMode]
         Blend SrcAlpha OneMinusSrcAlpha
 
         Pass
         {
         CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
 
             #include "UnityCG.cginc"
             #include "UnityUI.cginc"
             
             struct appdata_t
             {
                 float4 vertex   : POSITION;
                 float4 color    : COLOR;
                 float2 texcoord : TEXCOORD0;
             };
 
             struct v2f
             {
                 float4 vertex   : SV_POSITION;
                 fixed4 color    : COLOR;
                 half2 texcoord  : TEXCOORD0;
                 float4 worldPosition : TEXCOORD1;
             };
             
             fixed4 _Color;
             fixed4 _TextureSampleAdd;
             v2f vert(appdata_t IN)
             {
                 v2f OUT;
                 OUT.worldPosition = IN.vertex;
                 OUT.vertex = mul(UNITY_MATRIX_MVP, OUT.worldPosition);
 
                 OUT.texcoord = IN.texcoord;
                 
                 #ifdef UNITY_HALF_TEXEL_OFFSET
                 OUT.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
                 #endif
                 
                 OUT.color = IN.color * _Color;
                 return OUT;
             }
 
             sampler2D _MainTex;
             fixed4 frag(v2f IN) : SV_Target
             {
                 return (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
             }
         ENDCG
         }
     }
 }