There is no biblical evidence that the command to make disciples requires them to be members of your church. The fields are indeed white unto harvest if you don’t care who gets the credit other than the Holy Spirit. It is critical that your members be active in this harvest and beginning in your city is a great place to start. This post by Lizzie Ng is excellent:
“There’s more happening in your city than meets the eye. It can be easy to think God’s activity is confined to what we see in our single church congregation or non-profit organization. But do you know how to view God at work at work to reach your city? Our team—City Gospel Movements at Palau—champions leaders who are not content running programs in the four walls of their church. These leaders are restless to see local churches unite and work together for the peace and prosperity of their city.”