Not sure where you got your info, but the Latin Mass wasn't "written in 1570" with Quos Primas... It was merely standardized. The Mass was originally in Greek because that's what people commonly spoke in the Roman Empire in the First Century. Once Latin replaced Greek as the common tongue in the West (still in Antiquity) the Mass started being celebrated in Latin. By the late 4th century (around the same time the Catholic Church canonized the Bible) the Mass was said in the Western Church in Latin, and this remained universally true until 1964...

And to answer your question, St. Paul said to hold fast to our Traditions. from the late 300s to the 1960s, Western Christians were able to participate in the Latin Mass and knew what was happening, so why change it? Also, Latin, in addition to Greek and Hebrew, are all holy languages because those were the 3 languages written on the cross with the words "Jesus [of] Nazareth King [of the] Jews". In the Eastern Church they still use Greek in their Liturgy, so why shouldn't the Western Church still use Latin?

Not sure where you got your info, but the Latin Mass wasn't "written in 1570" with Quos Primas... It was merely standardized. The Mass was originally in Greek because that's what people commonly spoke in the Roman Empire in the First Century. Once Latin replaced Greek as the common tongue (still in Antiquity) the Mass started being celebrated in Latin. By the late 4th century (around the same time the Catholic Church canonized the Bible) the Mass was said in the Western Church in Latin, and this remained universally true until 1964...

And to answer your question, St. Paul said to hold fast to our Traditions. from the late 300s to the 1960s, Western Christians were able to participate in the Latin Mass and knew what was happening, so why change it? Also, Latin, in addition to Greek and Hebrew, are all holy languages because those were the 3 languages written on the cross with the words "Jesus [of] Nazareth King [of the] Jews". In the Eastern Church they still use Greek in their Liturgy, so why shouldn't the Western Church still use Latin?

Not sure where you got your info, but the Latin Mass wasn't "written in 1570" with Quos Primas... It was merely standardized. The Mass was originally in Greek because that's what people commonly spoke in the Roman Empire in the First Century. Once Latin replaced Greek as the common tongue (still in Antiquity) the Mass started being celebrated in Latin. By the late 4th century (around the same time the Catholic Church canonized the Bible) the Mass was said in the Western Church in Latin, and this remained universally true until 1964...