The poor peasant, St. Juan Diego is an unlikely candidate to be a saint. What did he know about doctrine, dogma and the fine intricate details of the Church? Really nothing, but yet he was chosen, like St. Bernadette, like the three children of Fatima and like scores of others to have a private revelation of the Blessed Virgin Mary. And his world and the world he touched has never been the same.
God gifted St. Juan with tremendous faith especially in Christ truly present in the Most Holy Eucharist. Did he fully understand the Tridentine Latin Mass? Could he always hear the priest praying the words of the Mass? More than likely no, but St. Juan knew that our Lord was present and that the Lord's presence also brings salvation. What more did he need?
The majority of the great saints of the Church were formed in the Tridentine Latin Mass. Just as with the 1970 Mass, the Lord is present. Do we see Him? And seeing Him do we follow?