About Galatians 5 here and including 1 Corinthians 6, as well, here… in the other conversation:
The ‘rules’ show us what love looks like and what to test ourselves against, where we fall short. A summary (that @Mervin_Bitikofer ‘liked’, maybe out of weariness as much as in agreement ; – ) was my post #294, not too far above.
in Gal 5 and 1Cor 6, Paul warns believers that their sins (ie, not keeping God’s laws) can result in them not inheriting the kingdom of God;
1John 2:3-6 says, “He who says ‘I know him’ but disobeys his commandments is a liar, and the truth is not in him”;
If you don’t keep God’s laws you cannot be justified: ”a man is justified by works and not by faith alone” … “faith without works is dead” (James 2:24, 26);
the book of Revelation describes God’s people as those who keep the commandments of God and have faith in Jesus (Rev 12:17, 14:12). Sounds like obeying God’s laws is pretty important.
None of what I just said contradicts any of that, although where you say “Paul warns believers” I would suggest that the warnings are really for the unbelievers among them (but the believers needed to examine themselves).
Paul’s severe warnings (Jesus gives some, as well!) are for those who think they are Christians. There were hypocrites and ‘mere professors’ even in the early church. Paul’s warnings say, in effect, if your behaviors are still evil then they reflect your evil heart and your ‘faith’ is dead, and you cannot be justified (as an adjective) – you are not, you cannot be a justified person, and cannot be justified (as a transitive verb) in that condition.