The Traditional Mass was codified in year 1570 by Saint Pope Pius V after the Council of Trent, under the name of “Tridentine Mass”. This mass was the only version celebrated in the whole world until 1969. It was based from the traditional way of early Christians and probably from the apostles. Before St. Pope Pius V codified the Tridentine Mass, Protestant Reformation kept pushing their heretic ways to the Catholic Church, one of their main agenda was to reform the Holy Mass according to their ways. For example, the priest together with the people is facing the altar, the Protestants wanted the priest to face to the people because they think that it is disrespectful to the people. They neglected the symbolism of the facing the altar is “Facing God”. Another problem is that every priestly order or places have their own different version of the mass, and the prayers are not properly translated which makes the protestants attack the Catholic Church including how the mass was conducted.
To fight the Protestant reformation, the Catholic Church formed the Council of Trent in 1545 for Counter-Reformation. Then in 1570, Saint Pope Pius V codified Tridentine Mass with a respect for the tradition. In this mass, Latin was the only language to be used except the Alleluia and Kyrie Eleison (Lord have mercy). It was the only version to be celebrated in every church in the world.
Then in year 1969, under Vatican II Council, Pope Paul VI reformed the Mass and called it was called the “Novus Ordo Mass” which has made many changes in the mass, like the priest was now facing the people, and the Latin language was no longer in use. But, one archbishop, Marcel Lefebvre wanted to maintain and celebrate the Tridentine Mass, this leads him to form the Priestly Society of Saint Pius X. Today, the Tridentine Mass is still celebrated and it is now called “The Traditional Mass”, “Latin Mass” or the “Extraordinary form of the mass”.
So, is the Traditional Latin Mass still valid? Yes and will always be valid and essential until the end of time.