You might get a better context with Hebrews 10:19-31, it is a paragraph I believe.
or the entire chapter?
I am not arguing against reading the entire chapter.
Here is a key part of that chapter 10
4 For it is impossible for the blood of bulls and goats to take away sins. 5 Therefore, when He comes into the world, He says,
“You have not desired sacrifice and offering,
But You have prepared a body for Me;
6 You have not taken pleasure in whole burnt offerings and offerings for sin.
7 Then I said, ‘Behold, I have come
(It is written of Me in the scroll of the book)
To do Your will, O God.’”
8 After saying above, “Sacrifices and offerings and whole burnt offerings and offerings for sin You have not desired, nor have You taken pleasure in them” (which are offered according to the Law), 9 then He said, “Behold, I have come to do Your will.” He takes away the first in order to establish the second.
So that is the end of the sacrificial system and so also the role of earthly priests in administering those sacrifices as Heb 7 also pointed out previously
10 By this will, we have been sanctified through the offering of the body of Jesus Christ once for all time.
The once for all time - sacrifice of Christ completed at the cross is the point in that verse above. Not an ongoing one, not one we can recreate
11 Every priest stands daily ministering and offering time after time the same sacrifices, which can never take away sins; 12 but He, having offered one sacrifice for sins for all time, sat down at the right hand of God, 13 waiting from that time onward until His enemies are made a footstool for His feet. 14 For by one offering He has perfected for all time those who are sanctified.
Not repeated "offering" but rather "once for all" -- by "ONE offering" not many times repeated - but once offered. And then Jesus "sits down" which means no more participation at all in that sacrifice in making it , in repeating it in offering it up to God as He did on the cross (on the altar of burnt offering symbolically as is the case with all sin offerings according to Heb 7)
15 And the Holy Spirit also testifies to us; for after saying,
BTW - I appreciate these details in your verses that you selected out of the chapter -
Hebrews 10:19-39
19 Therefore, brothers and sisters, since we have confidence to enter the holy place by the blood of Jesus, 20 by a new and living way which He inaugurated for us through the veil, that is, through His flesh, 21 and since we have a great priest over the house of God, 22 let’s approach God with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water. 23 Let’s hold firmly to the confession of our hope without wavering, for He who promised is faithful; 24 and let’s consider how to encourage one another in love and good deeds, 25 not abandoning our own meeting together, as is the habit of some people, but encouraging one another; and all the more as you see the day drawing near.
IN that example (as noted in my previous post with other verses in the same chapter) - the "we", the "us" and "our" are fellow Christians , believers. And the point is to persevere in the right path - so it argues against leaving it.
26 For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a terrifying expectation of judgment and the fury of a fire which will consume the adversaries. 28 Anyone who has ignored the Law of Moses is put to death without mercy on the testimony of two or three witnesses. 29 How much more severe punishment do you think he will deserve who has trampled underfoot 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?
This section above is that same example above where those who are forgiven and saved and on the right path - fall into rebellion, turning against God and choosing rebellion against the Word of God instead
30 For we know Him who said, “Vengeance is Mine, I will repay.” And again, “The Lord will judge His people.” 31 It is a terrifying thing to fall into the hands of the living God.
32 But remember the former days, when, after being enlightened, you endured a great conflict of sufferings, 33 partly by being made a public spectacle through insults and distress, and partly by becoming companions with those who were so treated. 34 For you showed sympathy to the prisoners and accepted joyfully the seizure of your property, knowing that you have for yourselves a better and lasting possession.
So here we have examples of fellow Christians doing the right thing, saved and being on the right path in vs 26-27
35 Therefore, do not throw away your confidence, which has a great reward. 36 For you have need of endurance, so that when you have done the will of God, you may receive what was promised.
37 For yet in a very little while,
He who is coming will come, and will not delay.
38 But My righteous one will live by faith;
And if he shrinks back, My soul has no pleasure in him.
39 But we are not among those who shrink back to destruction, but of those who have faith for the safekeeping of the soul
Paul's warning is specifically to the group he is writing to - those on the right path being warned against falling away.
"shrinks back" is very specifically identifying someone doing the right thing who then "shrinks back" from that right course from that approved condition. Instead of speaking to the "never saved" or "never on the right path" person who "Falls away from doing the wrong thing" it is speaking to the person on the right path who are in the right condition failing to continue in that right path, right condition before God and instead "Shrinking back" --