What many people fail to realize when they read those references to the early Christians as ‘saints’, is that at that point in time, the immensely strong faith of many of those very holy individuals was very much the same as the faith of those that the Catholic Church recognizes in modern times as Canonized Saints, especially the Apostles and those that were most closely associated with them. They performed amazing miracles of healing, conversion, etc., on a daily basis. I have no doubt that they often saw visions and communicated with Heavenly beings, such as angels and other Saints that were already in Heaven.
They lived extremely holy lives of perfect purity of mind, body and intention, and did not fall back into their previous lives of sin, once they were converted and Baptized into the Church of Jesus Christ. Since they were so very close to Jesus, Himself, they were unmovable in their faith in Him, and in what He had taught them. Therefore, they were actual living saints in the truest sense of the word. They had already reached such a high level of perfection and sanctity, that nowadays is almost impossible to find in any living Christian, no matter how holy they might seem to be (except in very rare cases like Padré Pio), that they were, in fact, true ‘saints’ while they were still walking the earth.