So let's look at the passage you quote.
2 Thessalonians 2:13-15 But we ought always to give thanks to God for you, brothers beloved by the Lord, because
God chose you as the firstfruitsto be saved, through sanctification by the Spirit and belief in the truth.
To this he called you through our gospel, so that you may obtain the glory of our Lord Jesus Christ.
So then, brothers, stand firm and hold to the traditions that you were taught by us, either by our spoken word or by our letter.
First, what a great passage regarding God's election of his children.
Notice the Sovereignty of God's authority oozing from these verses.
Second, in light of God's authority and his choice of Paul as His Apostle to the Gentiles, Paul has set up traditions, such as requirements for elders and deacons (both, by the way, were to be married and have believing children, which Rome rejects for it's bishops). Paul is authorized to set these up as God's Apostle.
What Paul does not say is that the Bible (scripture) is tradition. In 2 Timothy 3:16 he tells us it is profitable for doctrine, instruction and reproof. In Hebrews 4 we read that it cuts through a person's heart like a double-edged sword.
You are stretching to claim the Bible is just another form of your church tradition.
First, Paul was an authorized Apostle. Apostolic succession is a made-up philosophy of your church to make their twisted traditions equal to or greater than scripture. Such a claim is a crock. Peter was never a bishop in Rome. The Apostles never started the church at Rome (Christians were already there before the Apostles arrived). And there is no teaching of Apostolic succession in scripture.
Ultimately, your church has no legitimacy and it's present traditions are a stumbling block to the gospel.
Here's an example posted by a Roman Catholic friend on Facebook.
Watch the video. Read the words. And see the worship of Mary with no glory given to God. A perfect example of idol worship.