The universal Catholic understanding is that the Old Testament cannot be correctly understood without the truth of Christ, and therefore without the New Testament. The Old Testament is, however, inerrant word of God in its entirety.
Further, the Holy Scripture cannot be understood without the study of patristic writing, in which all modern theological thought worth mentioning must be grounded.
To say that the Old Testament is “mere mythology” is aberrant and latecoming teaching.
That the Church is “in the mess today” is true. It is also true that allowing the desacralized Bible study by scholars and milkmaids alike, a Protestant heresy, is probably to blame for much of it.
Luckily, the Church doesn’t look to its modern pastors when they develop theories and theological fantasies. Those come and go. The Church remains because Christ and His saints in Heaven remain, our true Jerusalem.
A "Protestant heresy?" Before chr*stianity existed the Holy Torah was the birthright of every single Jew, from the King and the Kohen Gadol to the beggar on the streets. It was and is the duty of every Jew to study Torah--as a matter of fact, one of the mitzvot is that every Jew is required to write a Sefer Torah (though nowadays this is usually accomplished by either hiring a sofer to write one on one's behalf or in writing a single letter, since very letter in the Torah is equivalent to the entire thing), though in ancient times people probably wrote their on Torahs in their entirety.
Catholics look down on "brain-dead bibliolators" who believe in the Bible for no other reason than that they believe in it, but Catholicism's faith J*sus, though not held because "the Bible says so," is just as groundless and fideistic.