First, John Mark departs from them.
Acts 13:13 Now when Paul and his company loosed from Paphos, they came to Perga in Pamphylia: and John departing from them returned to Jerusalem.
You only learn how bad that really was in Acts 15.
35 Paul also and Barnabas continued in Antioch, teaching and preaching the word of the Lord, with many others also.
36 And some days after Paul said unto Barnabas, Let us go again and visit our brethren in every city where we have preached the word of the Lord, and see how they do.
37 And Barnabas determined to take with them John, whose surname was Mark.
38 But Paul thought not good to take him with them, who departed from them from Pamphylia, and went not with them to the work.
39 And the contention was so sharp between them, that they departed asunder one from the other: and so Barnabas took Mark, and sailed unto Cyprus;
40 And Paul chose Silas, and departed, being recommended by the brethren unto the grace of God.
41 And he went through Syria and Cilicia, confirming the churches.
Barnabas was a respector of persons towards John Mark, while at the same time, John Mark was a respector of persons because he didn’t want to do the work in Pamphylia. Barnabas wanted to be nicey-nice with John Mark.
From this, you would say that John Mark was not profitable for the ministry.
6 For I am now ready to be offered, and the time of my departure is at hand.
7 I have fought a good fight, I have finished my course, I have kept the faith:
8 Henceforth there is laid up for me a crown of righteousness, which the Lord, the righteous judge, shall give me at that day: and not to me only, but unto all them also that love his appearing.
9 Do thy diligence to come shortly unto me:
10 For Demas hath forsaken me, having loved this present world, and is departed unto Thessalonica; Crescens to Galatia, Titus unto Dalmatia.
11 Only Luke is with me. Take Mark, and bring him with thee: for he is profitable to me for the ministry.
12 And Tychicus have I sent to Ephesus.
Later, John Mark is profitable because he chose to enter back into the work.