Paul says in Romans 5:11. ..through our Lord Jesus Christ, we have the atonement.
We do not have "an atonement", we have the atonement
Jesus' ordainment as High Priest was from God.
Hebrews 7:15-28 gives all the reasons why Christ and Christ alone is able to make atonement.
Hebrews 9:11-28 lists all the reasons why Christ was the perfect offering for sins.
Hebrews 10:1-18, shows why the sacrifice was once, for all
Hebrews10:12, He offered one sacrifice for sins, forever
You're just nitpicking without actually reading the article, aren't you?