I think I see where I am confusing you.
Let me help you understand my own perspective and see in what areas agreement is found.
First the forensics, then the applications.
History teaches that the Roman crucifixion was not a blood letting event. Truly, they wanted the person to last as long as possible that the torture would be prolonged for days.
The blood on the cross was certainly there, but far more was slathered in the judgment halls and along the roads. (Isaiah 53)
It is that shedding of blood that is for the remission of sins, the sprinkling upon the alter was the presentation of the shed blood not the shedding of blood.
What took place then upon the cross was the death. How the savior died, the validation of death by the wounded side of which blood and water escaped. They did not pump and were not pushed other than by the force of air trapped in the lungs as the lungs deflated. The natural circulation of blood had no pressure. The flow was as one might expect from anything dead - gravity not pressure. Such as one might expect when fresh but dead fish are cleaned, blood smeared.
The cross was the tool of death, just as the tomb was the tool of resurrection. Without either, the atonement for believers could not be accomplished.
Therefore, when I look upon the crucifixion, I do not limit it to only the cross and tomb, but see that it begins in the garden where sin first occurred. It encompasses the religious and civil authorities, the common people. “It is finished” was the pronouncement of the Savior for himself as it pertained to His sacrifice, but it was not finished for humankind. The blood was shed, the lamb was slain, yet there was more to be done. More the OT pictures presented
The vail rent, the body removal, the presence in paradise, ... much more than I have strength to write.
Now to your question (statement).
The shed blood certainly (as John states) paid for all sin, of all creation. However, that does not automatically lead to universal salvation. To think that it does is to be far too narrowly presenting the atonement as the OT presented in picture form.
There was also washings, garment changes, public presentations, scapegoats, more sacrifices, cleansings, so much more.
Redemption is specific. It is particular to those to whom the Father gives to the Son. To those in whom God gives the power to believe and so done demonstrate He adopted them.
Redemption is based upon the death and resurrection, for the blood was shed for the universe, but Christ died and rose for His sheep.
Now do not become too exercised in this matter, for I see no reason to trouble your spirit.
I am merely hoping to make what my Redeemer accomplished more precious as you continue your thinking.
The cross is certainly not wonderful, but was most wondrous.
What he endured prior to the cross is unimaginable.
The care of taking him from the cross to the tomb and leaving him there, what glory it brings.
His presence in paradise to preach, his presence before the Father to grasp and remove the scroll, and so much more.
Foundational in this presentation is that found in Hebrews 9:
11But when Christ appeared as a high priest of the good things that have come, then through the greater and more perfect tent (not made with hands, that is, not of this creation)
12he entered once for all into the holy places, not by means of the blood of goats and calves but by means of his own blood, thus securing an eternal redemption.
13For if the blood of goats and bulls, and the sprinkling of defiled persons with the ashes of a heifer, sanctify for the purification of the flesh,
14how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to serve the living God.
15Therefore he is the mediator of a new covenant,
so that those who are called may receive the promised eternal inheritance, since a death has occurred that redeems them from the transgressions committed under the first covenant.
h16For where a will is involved, the death of the one who made it must be established.
17For a will takes effect only at death, since it is not in force as long as the one who made it is alive.
18Therefore not even the first covenant was inaugurated without blood.
19For when every commandment of the law had been declared by Moses to all the people, he took the blood of calves and goats, with water and scarlet wool and hyssop, and sprinkled both the book itself and all the people,
20saying, “This is the blood of the covenant that God commanded for you.”
21And
in the same way he sprinkled with the blood both the tent and all the vessels used in worship. 22Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.
23Thus it was
necessary for the copies of the heavenly things to be purified with these rites, but the heavenly things themselves with better sacrifices than these. 24For Christ has entered, not into holy places made with hands, which are copies of the true things, but
into heaven itself, now to appear in the presence of God on our behalf. 25Nor was it to offer himself repeatedly, as they high priest enters the holy places every year with blood not his own,
26for then he would have had to suffer repeatedly since the foundation of the world. But as it is, he has appeared once for all at the end of the ages to put away sin by the sacrifice of himself.
27And just as it is appointed for man to die once, and after that comes judgment,
28so Christ,
having been offered once to bear the sins of many (abundant, all, innumerable, numerous, enough,...), will appear a second time,
not to deal with sin but to save those who are eagerly waiting for him.
