You contend that since the OT priesthood received a detailed scriptural description, and since there is no description of equal length of an NT priesthood, they the NT priesthood must not exist.
Why is God bound in this way? We have skeletal scripture references to the NT priesthood combined with Christ’s spoken instructions to His Apostles. Secular historians have no problem acknowledging the existence of the Christian priesthood from the very beginning. It seems you are biased against the facts backed by empirical evidence that unbiased scholars consider irrefutable.
Protestants study the heroes of Old Testament history. Why are they so afraid to study the New? Do you know or care about the opinions of the Early Fathers on Apostolic succession?
You seek to defend Paul against Matthias but Paul was never in competition with Matthias. While there were only twelve original Apostles, there is no such numerical limit on Apostolic successors (bishops). Matthias was a bishop, not an additional Apostle like Paul. All public revelation ended with the death of the last Apostle.
There is NO discussion of a priesthood offering a sacrifice for sin in the New Testament. On the contrary, it is specifically and explicitly REJECTED:
8 When he said above, “You have neither desired nor taken pleasure in sacrifices and offerings and burnt offerings and sin offerings” (these are offered according to the law), 9 then he added, “Behold, I have come to do your will.” He does away with the first in order to establish the second. 10 And by that will we have been sanctified through the offering of the body of Jesus Christ once for all.
11 And every priest stands daily at his service, offering repeatedly the same sacrifices, which can never take away sins. 12 But when Christ had offered for all time a single sacrifice for sins, he sat down at the right hand of God, 13 waiting from that time until his enemies should be made a footstool for his feet. 14 For by a single offering he has perfected for all time those who are being sanctified.
15 And the Holy Spirit also bears witness to us; for after saying,
16 “This is the covenant that I will make with them
after those days, declares the Lord:
I will put my laws on their hearts,
and write them on their minds,”
17 then he adds,
“I will remember their sins and their lawless deeds no more.”
18 Where there is forgiveness of these, there is no longer any offering for sin.
19 Therefore, brothers, since we have confidence to enter the holy places by the blood of Jesus, 20 by the new and living way that he opened for us through the curtain, that is, through his flesh, 21 and since we have a great priest over the house of God, 22 let us draw near with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water. 23 Let us hold fast the confession of our hope without wavering, for he who promised is faithful. - Heb 10
Apostles, teachers and shepherds are given by God, not chosen by men. Man can only acknowledge God’s choice.
“7 But grace was given to each one of us according to the measure of Christ’s gift. 8 Therefore it says,
“When he ascended on high he led a host of captives,
and he gave gifts to men.”
...11 And he gave the apostles, the prophets, the evangelists, the shepherds and teachers, 12 to equip the saints for the work of ministry, for building up the body of Christ, 13 until we all attain to the unity of the faith and of the knowledge of the Son of God...” - Ephesians 4
“27 Now you are the body of Christ and individually members of it. 28 And God has appointed in the church first apostles, second prophets, third teachers, then miracles, then gifts of healing, helping, administrating, and various kinds of tongues. 29 Are all apostles? Are all prophets? Are all teachers? Do all work miracles? 30 Do all possess gifts of healing? Do all speak with tongues? Do all interpret? 31 But earnestly desire the higher gifts.” - 1 Cor 12