I’d be a little more careful in how I describe the relationship between the two covenants. Fulfilment is not the same as abolition. It is about perfecting the imperfect, completing the incomplete but not about throwing the old aside or denying it’s goodness.
The mitzvot of the Torah dealing with ceremonial, ritual purity/dietary matters have not been “abolished” (hard supersessionism, which the church rejects today), it is merely the case that people - whether ethno-culturally Jewish or Gentile - who are baptised members of the church, are redeemed and justified by a living faith in Jesus (the fullness of divine revelation), rather than through those works of the law.
The mitzvot themselves were never binding upon Gentiles in the first place and St. Paul cautions that for Gentiles to subject themselves to such mitzvot would be akin to denying the efficacy of Christ’s sacrifice (the heresy of “Judaization”).
However, this does not mean that Jews can no longer observe these divinely-ordained laws which God (in our theological understanding) revealed specifically for the children of Israel that they might be a “light unto the nations”.
St. Paul actually writes:
1 Corinthians 7:18-20 [ESV]: “Was anyone at the time of his call already circumcised? Let him not seek to remove the marks of circumcision. Was anyone at the time of his call uncircumcised? Let him not seek circumcision…Each one should remain in the condition in which he was called”
Jews are born as Jews by upbringing and ethnicity, Gentiles as Gentiles by upbringing and ethnicity (i.e. Irish Catholics, Mexican Catholics, Polish Catholics, Melkite Catholics).
We are each entitled to remain “as we were called”, at least so far as our conscience so dictates:
“I know and am persuaded in the Lord Jesus that nothing is unclean in itself, but it is unclean for anyone who thinks it unclean.” (Romans 14:14)
If an ethnic Jewish believer in Christ, on the other hand, freely chooses not to be Torah-observant (i.e. decides that he doesn’t consider non-kosher food unclean, or himself impure for not following the purity laws of his heritage etc.) then he or she equally has that liberty.
The moral laws of the Torah are eternally binding, the ceremonial/cultic/purity/dietary laws were only ever intended for Jews (then and now).
To be precise, the only laws which Christians regard as “abolished” are the Temple blood sacrifices (the grain offerings could theoretically still be offered up if there were a re-constructed Third Temple), because Christ’s offering up of his body and blood as eternal high priest in the Eucharist have replaced them, and I would personally say the judicial/penal regulations too as evidenced by the pericope adulterae, which reflected the needs / social limitations of the more primitive time in which they were revealed and would be excessively harsh by today’s standards, ordained therefore only for the ancient Israelites.