Bl John XXIII believed Latin was important and stated so in his encyclical
Veterum Sapientia.
I have included the link to the encyclical at the bottom of this post. Here are some excerpts:
*But amid this variety of languages a primary place must surely be given to that language which had its origins in Latium, and later proved so admirable a means for the spreading of Christianity throughout the West. *
And since in Gods special Providence this language united so many nations together under the authority of the Roman Empire— and that for so many centuries— it also became the rightful language of the Apostolic See.3 Preserved for posterity, it proved to be a bond of unity for the Christian peoples of Europe.
Of its very nature Latin is most suitable for promoting every form of culture among peoples. It gives rise to no jealousies. It does not favor any one nation, but presents itself with equal impartiality to all and is equally acceptable to all. (emphasis mine)
*Nor must we overlook the characteristic nobility of Latin formal structure. **Its “concise, varied and harmonious style, full of majesty and dignity”***4 makes for singular clarity and impressiveness of expression. (emphasis mine)
*Thus the “knowledge and use of this language,” so intimately bound up with the Church’s life, **“is important not so much on cultural or literary grounds, as for religious reasons.”***6 These are the words of Our Predecessor Pius XI, who conducted a scientific inquiry into this whole subject, and indicated three qualities of the Latin language which harmonize to a remarkable degree with the Church’s nature. **“For the Church, precisely because it embraces all nations and is destined to endure to the end of time . . of its very nature requires a language which is universal, immutable, and non vernacular.”**7 (emphasis mine)
Furthermore, the Church’s language must be not only universal but also immutable. Modern languages are liable to change, and no single one of them is superior to the others in authority. **Thus if the truths of the Catholic Church were entrusted to an unspecified number of them, the meaning of these truths, varied as they are, would not be manifested to everyone with sufficient clarity and precision. **(emphasis mine)
Finally, the Catholic Church has a dignity far surpassing that of every merely human society, for it was founded by Christ the Lord. It is altogether fitting, therefore, that the language it uses should be noble, majestic, and non-vernacular. (emphasis mine)
*In addition, the **Latin language "can be called truly catholic."10 It has been consecrated through constant use by the Apostolic See, the mother and teacher of all Churches, and must be esteemed “a treasure . . . of incomparable worth.”***11. It is a general passport to the proper understanding of the Christian writers of antiquity and the documents of the Church’s teaching.12 It is also a most effective bond, binding the Church of today with that of the past and of the future in wonderful continuity. (emphasis mine)
Latin was extremely important to Bl John XXIII, the Pope who convened the Second Vatican Council.
catholicculture.org/docs/doc_view.cfm?recnum=1160