In Lumen Fidei, the first encyclical of his pontificate (a collaborative effort with his predecessor Benedict XVI), Pope Francis has this to say about the importance and role of Tradition in the Church:
It is through the apostolic Tradition preserved in the Church with the assistance of the Holy Spirit that we enjoy a living contact with the foundational memory. [LF §40]
How do we know that the Church has preserved Sacred Tradition? Because the Holy Spirit has protected and defended her from error. There is another sense in which the response to this challenge is glaringly obvious (to me, now, at any rate): the Church is the Body of Christ, and together with her Head the Lord Jesus Christ forms one mystically united Body. In this sense, it is impossible for the Church to err in matters of faith and doctrine because her union with Christ would necessarily imply that Christ Himself has erred, and this is impossible:
Christ and his Church thus together make up the “whole Christ” (Christus totus). [CCC §795; emphasis in original]
These facts ensure that (as Pope Francis wrote) “we enjoy a living contact with the foundational memory.” The proper interpretation of God’s revelation is not left to scholars trying to make sense of 2000+ year old manuscripts; it is not left to individuals (which inescapably reduces to subjectivism). Rather, we have a living memory of what Christ revealed, and a living memory of what it means, and it is assured by the Holy Spirit. The light of faith is preserved in the Church by God.