The New Covenant is not like the Old Covenant (HEB 8).
Entry into the Old Covenant did not require faith in God; most of the people in that community were unbelievers. All they (the males) needed for entry was circumcision of their flesh. Entry into the New Covenant comes only to those who believe on the Son of God (John 10), who have been circumcised of the heart, not made with human hands (Col 2).
The mediator of the New Covenant is not another in the type of Moses – a servant in God’s house (Heb 3). He is the Son and Lord of the house!
God does not change our old stone into a new heart of flesh, He removes the heart of stone and implants a heart of flesh (Jer 31).
God does not improve the stone temple in which Israel worshiped Him, His redeemed are the temple of God! (1 Cor 3, 1 Pet 2)
The New Covenant does not have a priest after the order of Aaron but after the order of Melchizedek, who had no genealogy (Heb 7). This was not merely a change in/within the priesthood, it was a change OF priesthood; the nature of the priesthood is different (Heb 8).
The sacrifices of the Old Covenant could never take away sin, but only cover them for a season. The sacrifice of the New Covenant takes away all the sins of all the people in that covenant community, showing the weakness of the law and the superiority of the oath and promise (Heb 7). The nature of the sacrifices in the two covenant are not the same.
When the passage (Heb 7) says that a change of the priesthood mandates a change OF the law, the same nature of change is at hand. The law given to the Old Covenant community is not suited for the New Covenant community. A new type of law is required – one reflecting the priesthood as well as the community, which is 100% redeemed and dwelt by the Holy Spirit.
The law written on the flesh hearts of the saints is not the legal code with warnings and penalties, issued from the fiery mount (HEB 12). The law written on the hearts of the redeemed is the perfect law, the law of liberty (James 1), the royal law (James 2), the law of Christ (Gal 6). The law of Moses COMMANDED its people to rest from the work of providing for themselves (Ex 20). The law of Christ PROVIDES rest for the redeemed, no longer working to prove themselves to God, but serving one another, bearing burdens, loving others as Christ has loved us.
No legal code with threats and penalties for a stiff-necked and rebellious people but a new creature (Gal 6, 2 Cor 5) that loves God and others, in which the Spirit of God dwells, to equip and will His people to that which pleases Him (Phil 2).