the flesh itself is sin.
sin is not just a system or an action.
the corruption caused by the fall
is cosmological not just a mental state.
if you go and enjoy this world and body,
that is the sin realm being enjoyed.
I think this is what
@SovereignGrace is talking about below that we can live by the flesh(carnal nature) or by the spirit to either glorify God or self-our fallen sinful and corrupt nature. Paul is contrasting the two and those who practice or continue in the flesh will not inherit the kingdom but only those who live by the spirit will.
Galatians 5:19-22
The acts of the flesh are obvious: sexual immorality, impurity and debauchery; 20 idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions 21 and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God.
22
But the fruit of the Spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, 23 gentleness and self-control. Against such things there is no law. 24 Those who belong to Christ Jesus have crucified the flesh with its passions and desires. 25 Since we live by the Spirit, let us keep in step with the Spirit. 26 Let us not become conceited, provoking and envying each other.
Galatians 6:8
For he that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit shall of the Spirit reap life everlasting.
Romans 8:5
Those who live according to the flesh set their minds on the things of the flesh; but those who live according to the Spirit set their minds on the things of the Spirit.
1 Corinthians 6:9
Do you not know that the wicked will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral, nor idolaters, nor adulterers, nor men who submit to or perform homosexual acts,
Colossians 3:5
Put to death, therefore, the components of your earthly nature: sexual immorality, impurity, lust, evil desires, and greed, which is idolatry.
Mark 7:21
For from within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery,
Matthew 15:19
For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, and slander
hope this helps !!!