It reflects that the apostles' understanding was that our Lord had established them in an apostolic office that continues after their death. There is nothing in the Scriptures to contradict this understanding. Where in the Bible does it say what they did was wrong? I will stand with the apostles and the Bible.
In Acts 15 there is no mention of apostolic succession nor instructions on how to appoint leaders.
It does show that the presbyters shared in the authority of the apostles in governing the Church. Sorry, but the Bible shows that the Holy Spirit teaches through the its officially appointed pastors, not that we as individuals are free to teach on their own contrary to them.
Yet Paul was not appointed by the disciples. And this is crucial to understand in that it shows God can and does choose who He wants to be in the ministry.