The irony is that those who at first did not believe became fathers of faith for all who would later believe (Augustine).
What the Apostles, themselves had seen and not believed, the Gentiles would later believe without seeing (Jerome).
The unity of the whole body of Christ derives from its continuity with the teachings of the Apostles (Tertullian).
The gifts of casting out demons were given not exclusively to the first apostolic generation but also to the continuing apostolate. Each believer receives gifts from the Father and Son through the Spirit according to each one’s capacity to receive (Ambrose).
There will be accompanying signs. These were needed at the Church’s beginnings. The new faith needed to be nourished by miracles to grow. When the elements of faith have taken deep roots in us, there is no need of continuing miracles (Gregory the Great).