You mention Romans 8:8, but that must be read in the context of Romans 7. Where Paul is speaking of the unregenerated nature, the fact we are sold under sin. It tells us clearly the natural man can delight in God's words when he/she hears them. But that the flesh overpowers us. This shows us that man can respond to things such as faith, and even try to be obedient, which is what Jesus said leads to enlightenment.
John 14:22-24 Judas (not Iscariot) said to Him, "Lord, how is it that You will manifest Yourself to us, and not to the world?" Jesus answered and said to him, "If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our home with him. He who does not love Me does not keep My words; and the word which you hear is not Mine but the Father's who sent Me.
Rom 7:14-23 For we know that the law is spiritual, but I am carnal, sold under sin. For what I am doing, I do not understand. For what I will to do, that I do not practice; but what I hate, that I do. If, then, I do what I will not to do, I agree with the law that it is good. But now, it is no longer I who do it, but sin that dwells in me. For I know that in me (that is, in my flesh) nothing good dwells; for to will is present with me, but how to perform what is good I do not find. For the good that I will to do, I do not do; but the evil I will not to do, that I practice. Now if I do what I will not to do, it is no longer I who do it, but sin that dwells in me. I find then a law, that evil is present with me, the one who wills to do good. For I delight in the law of God according to the inward man. But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.