Titus 1:9 He must hold firmly to the trustworthy message as it has been taught, so that he can encourage others by sound doctrine and refute those who oppose it.
Titus 2:1 You must teach what is in accord with sound doctrine.
1 Tim 6:3 If anyone advocates a different doctrine, and does not agree with sound words, those of our Lord Jesus Christ, and with the doctrine conforming to godliness, 4 he is conceited and understands nothing; but he has a morbid interest in controversial questions and disputes about words, out of which arise envy, strife, abusive language, evil suspicions, 5 and constant friction between men of depraved mind and deprived of the truth, who suppose that godliness is a means of gain.
1 Tim 1:8 We know that the law is good if one uses it properly. 9 We also know that law is made not for the righteous but for lawbreakers and rebels, the ungodly and sinful, the unholy and irreligious; for those who kill their fathers or mothers, for murderers, 10 for adulterers and perverts, for slave traders and liars and perjurers – and for whatever else is contrary to the sound doctrine 11 that conforms to the glorious gospel of the Blessed God, which He entrusted to me.
2 Jn 1:9 Anyone who runs ahead and does not continue in the teaching of Christ does not have God; whoever continues in the teaching has both the Father and the Son. 10 If anyone comes to you and does not bring this teaching, do not take him into your house or welcome him. 11 Anyone who welcomes him shares in his wicked work.
Doctrine. It's kind of important.
Yes, doctrine can be important. Wasting time over a rough doctrinal equivalent of how many angels can dance on the head of a pin is not. I see lots of scripture posted without explanation of relevance to a given topic. I see scripture misused, when with some careful study it says something other than what itis being used to support, and people acting offended if they get called on such behavior. That is pure waste of time on what is called "doctrine" and is actually self-aggrandizement.
By the way, what was Paul's specific gospel that he needed approved since the acceptance of the Gentiles was made clear previously even in Acts, as was acting outside the Mosaic law, and that Gentiles could be accepted without them having to follow the Mosaic law was documented in the Dead Sea Scrolls? Unless that question can be answered, with clear support from the scriptures, you might be misrepresenting some of the passages you cited. And here bear in mind that it certainly appears that at least two gospels were changed from their original texts, but exactly how is unclear (textual criticism to use the academic term).