Now we would see that preaching the gospel to the world and to all nations is amazing and besides not that it can not be done one on one but it is really amazing and better to do it in a congregation or with lots of people at once.
Now let look into the book of ISAIAH 49:3 which it says let all the nations be gathered and let the people be assembled: who among them can declare this, and show us former things? Let them bring forth their witnesses, that they may be justified; or let them hear and say, It is Truth, which implies that preaching the gospel to greater Congregations which includes gathering of all nations of all nations is better because it allows the gospel to be fully spread to all at once.
The salvation of the Lord you see is free to all and must be spread to all even our Dear Lord Jesus Christ said, make disciples in all nations baptizing them in the name of the Father, and of the Son, and of the Holy Spirit and teaching them to observe all things whatsoever I have commanded you: and, lol, I am with you always, even unto the end of the world. Amen. MATTHEW 28:20
Which implies we have to spread the awesomeness of the Lord in all nations of the world