The article starts with a specious conflation, so how is it a ‘good’ article? The Catholic Church is not the whole body of believers in Jesus Christ as Savior and Lord, so the starting premise is a deception perhaps.
In the context of the article, I will agree with you. The big "C" Catholic Church is Rome and while I believe that there is a remnant in that church, I too believe that it does NOT contain the whole body of believers.
However there is the small "c" catholic church which can be paraphrased as the "universal" church that does contain the whole of the body of Christ. Thus when we, as protestants, declare our faith using the Apostle's Creed, and we state that we "believe in the holy catholic church...". It does not mean that we are pledging allegiance to Rome, but rather acknowledging that we are members of a worldwide body and that we have communion with one another through Christ.