In Jesus’ time on earth when a Jew wrote to Jews about the Jewish religious community he used the term synagog and for the community at large ecclesia. When Paul as an apostle to the Gentiles wrote to those who followed The Way (an earlier term for Christianity), he used the term ecclesia for the religious community.
So in Matthew 18, when Jesus is talking about confronting the brother (adelphos – of the same womb), is he talking about the religious community or the church?
Ecclesia gets translated as church because it is the term Paul used for church later. But Matthew, a Jew writing a biography of Jesus aimed at his fellow Jews who is in the land of the Jews talking to other Jews, would probably use the term the way the Jews understood it. If I haven’t emphasized this enough, this is a Jewish context where the word ecclesia means the secular gathering, not the religious community.
The bottom line for this change in interpretation is that Jesus never gave any one authority to keep someone else out of heaven. He was saying that we need to confront those who are harming the community.
The guidelines are still important. Talk personally to someone first, then get a small group discussion that still keeps it confidential and only publicize it when there is an obvious impasse in the communication and the harmful action is continuing. It is not appropriate to publicly denounce someone that you have not talked to personally. This applies to politics as well as pulpits.