What Paul is explaining is that we sometimes, for some most often, choose instinctual pleasures when we know they are bad for us. Sometimes we do, sometimes we don’t.
Sometimes it is lack of knowledge, sometimes it is a habit. Man, unlike animals can over-ride instincts, sometimes.
We can also resist habitual actions long enough to build new habits which results in needing less self-control to resist instinctual pleasures. And the reverse, we can build bad habits. As the old man said “If you ride with the Devil enough times, sooner or later, he’s gonna wanna take the wheel.”
We are not perfect, but neither are we without choices. We do not have perfect self-control, but we can choose to improve it. We do not have perfect knowledge, but we can seek more. Different folks have different circumstances and abilities, but, given a reasonably sound mind, humans have a wider range of choices than, say, animals, who have none.
Your black and white world applies to animals who have no consciousness. But we are made in God’s image.
Not God by any stretch, but not pure animal either.
So sin is a habit???? Our Lord Jesus saw the human condition differently:
Mat 7:11 If you then, who are evil, know how to give good gifts to your children, how much more will your Father who is in heaven give good things to those who ask him!
Joh 2:24 But Jesus on his part did not entrust himself to them, because he knew all people
We are not perfect, but neither are we without choices.
We have choices. We by nature choose to do evil things because it is in our hearts. That is why we are not perfect. And God commands perfection.