Unity Naive Blur Shader (This shader is slow!!!)

naiveblur.shader

Shader "matheusfaria/NaiveBlur"
{
    Properties
    {
        _MainTex ("Base (RGB)", 2D) = "white" {}
        _Radius ("Blur Radius", Int) = 3
    }

    Category
    {
        Tags {
            "Queue"="Transparent"
        }

        SubShader
        {
            Pass
            {
                CGPROGRAM

                #pragma vertex vert
                #pragma fragment frag

                #include "UnityCG.cginc"

                sampler2D _MainTex;
                float4 _MainTex_ST;
				float2 _MainTex_TexelSize;

                int _Radius;

                struct v2f {
                    float4  pos : SV_POSITION;
                    float2  uv : TEXCOORD0;
                };

                v2f vert (appdata_base v)
                {
                    v2f o;
                    o.pos = UnityObjectToClipPos (v.vertex);
                    o.uv = TRANSFORM_TEX (v.texcoord, _MainTex);
                    return o;
                }

                half4 frag (v2f i) : COLOR
                {
                    half4 texcol = half4(0.0, 0.0, 0.0, 0.0);

                    for (int x  = -_Radius; x <= _Radius; ++x) {
                        for (int y = -_Radius; y <= _Radius; ++y) {
                            texcol += tex2D(
                                _MainTex,
                                float2(
                                    i.uv.x + x * _MainTex_TexelSize.x,
                                    i.uv.y + y * _MainTex_TexelSize.y
                                )
                            );
                        }
                    }
                    texcol /=  (_Radius * 2 + 1) * (_Radius * 2 + 1);

                    return texcol;
                }
                ENDCG
            }
        }
    }
}