The interpretation and practices of the jews. That doesn't mean that there is NO validity to the old testament. The example I've been using it is that of the Lord's holy days. You seem to be of the mindset that since the jews observed them, or since they were first record in the books of the old testament, that there must be something wrong with them.
For Christians, the OT is interepretd in light of the New Covenant. Once the New Covenant was formed, those who continue in the Old Covenant are left outside. That includes their practices.
The Jewish practices were established under the Old Covenant. They no longer apply to Christians, just as circumcision in the flesh, kosher foods, and all other customs practriced by the Jews don't apply. Accepting them would mean going back to the practices that the NT says are not part of the New Covenant. Why? Because they are not salivifc. The blood of the rams and bulls does not atone for anyone. Their sacrifice is a mere reminder of our sins, and imperfect attempt at obtaining absolution of our sins.
Modern Judaism, having no other choice, is closer to Christianity today because it offers prayers instead of symbolic carnal offerings and their consumption and disappearance, as a symbolic gesture of obliteration for our sins.
Christians are not required, bound or directed to follow the law. The law offers no salvation. The works of the law are dead. As one Calvinist site says -- it's about Grace, not race.