Romans 7:14-25 is mans struggle to keep the Law while still having "the flesh."
Since we've established that 'the flesh' is your flesh body with it's various yearnings and appetites, aroused and corrupted by the evil one, the failure in Romans 7 is because of the absence of the mind being set on the things of the Spirit, rather than the things of the flesh. That could be because you don't have the Spirit, obviously. But it could also mean you do have the Spirit but your mind is not educated in the things of the Lord, or you are not familiar with the Lord's help in the battle with sin.
The flesh/carnal nature was in opposition to the Law. This is why Jesus takes away the carnal flesh and writes His laws on our heart.
But you still sin. So how is that Jesus taking away the flesh/carnal nature? This only makes sense if you understand what the Bible says, that it is because you are still in unredeemed flesh that you still sin. And that you have to put your mind on heavenly things, the things of the Spirit, and rely on God to resist and not be defeated by the things of the flesh.
If anyone still relates to these verses, they haven't been born again of the Spirit.
Either that, or they are born again but have yet to learn what constitutes righteous behavior, and learn how to avail themselves of the Lord's help in overcoming temptation. Still being able to sin does not mean you are not born again. Living in sin and being characterized by it means you are not born again. Slavery to sin is the sign of unbelief, not still being able to sin.