Comment: You are failing to understand

With all due respect, you are not understanding what is being said in each case.
Read the verse in 2 Thessalonians carefully and you will see that Paul is refering to being taught by the Word of God both in the old and the new Testaments.

Jesus was pointing directly to the teachings and traditions of men in both Matthew 15 and in Mark 7.

Paul was pointing to the teachings taught of God through His prophets ( "the Word" in the Old Testament ) and through "our epistle" which is also given by God to the apostles such as Paul, Peter and others in the New Testament.

They are clearly different contexts.

Peace