The restoration of blood temple sacrifices and ordinances that were operative under the Old Covenant would entail rejecting the message of the gospel. All those things were mere pointers and found their fulfillment in Christ. To reject the gospel would be the greatest act of insolence possible against God, and hence a terrifying expectation of judgement awaits those who deliberately do such a thing. That was the purpose of the author posing this vividly phrased rhetorical question:
"Anyone who has set aside the Law of Moses dies without mercy on the testimony of two or three witnesses. How much severer punishment do you think he will deserve who has trampled under foot the Son of God, and has regarded as unclean the blood of the covenant by which he was sanctified, and has insulted the Spirit of grace?" (Hebrews 10:28-29)
If a man does not have faith in Jesus Christ, then it goes without saying that he cannot be saved as long as he remains in that state of heart. God no longer accepts Levitical offerings. He has already made His plan of redemption fully known in Christ (Hebrews 1:3).