When the Church speaks of “different groups,” it does not mean self-selected church groupings. Let’s read this brief section:
191. Catechesis, today, is confronted by subjects who, because of professional training or more broadly cultural formation, require special programmes. These include catechesis for workers, for professionals, for artists, for scientists and for university students. This is warmly recommended within the common journey of the Christian community. Clearly, all these sectors demand a competent approach and language adapted to those being catechized, while always maintaining fidelity to the message which catechesis transmits.(Cf. Catechesi Tradendae 59)
Even large parishes may struggle to find the resources to address some of these groups. There’s something to be said for cooperation across parish boundaries, within a diocese, and even among them.