Fallen man's will is not totally free, he cannot make the moral choice to be sinless. . .Adam could.
If Adam had a choice, and I agree he did, then God's sovereignty is not lessened by His allowing choice for people.
So there is no conflict with God's decree, and God allowing choice, within the parameters He ordains.
Now God certainly knew Adam and Eve would sin. And if the Lamb of God was slain from the foundation of the world, He then knew that redemption would involve sending His Son.
Man's free will is now limited by his sin nature.
It is quite true that the man in the flesh cannot please God.
Romans 8:7-8 7 Because the carnal mind is enmity against God; for it is not subject to the law of God, nor indeed can be. 8 So then, those who are in the flesh cannot please God. (NKJV)
Even in that passage, the solution is in Christ and what He did. We have to be in Christ and set our mind on the Spirit.
Romans 8:1-4 1 There is therefore now no condemnation to those who are in Christ Jesus, who do not walk according to the flesh, but according to the Spirit. 2 For the law of the Spirit of life in Christ Jesus has made me free from the law of sin and death. 3 For what the law could not do in that it was weak through the flesh, God did by sending His own Son in the likeness of sinful flesh, on account of sin: He condemned sin in the flesh, 4 that the righteous requirement of the law might be fulfilled in us who do not walk according to the flesh but according to the Spirit. (NKJV)
But, as
@Hoping2 referenced, God's solution to the problem of the fall is to repent, believe the Gospel, be Baptized into Christ's death, also be joined to His resurrection to new life. Then we can access that new life in the Spirit when we consider ourselves dead to sin. We can then bear fruit by the Spirit.
Luke 24:46-47 46 Then He said to them, “Thus it is written, and thus it was necessary for the Christ to suffer and to rise from the dead the third day, 47 and that repentance and remission of sins should be preached in His name to all nations, beginning at Jerusalem. (NKJV)
Acts 2:38-39 38 Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit. 39 For the promise is to you and to your children, and to all who are afar off, as many as the Lord our God will call.” (NKJV)
Acts 3:18-26
18 But those things which God foretold by the mouth of all His prophets, that the Christ would suffer, He has thus fulfilled. 19 Repent therefore and be converted, that your sins may be blotted out, so that times of refreshing may come from the presence of the Lord, 20 and that He may send Jesus Christ, who was preached to you before, 21 whom heaven must receive until the times of restoration of all things, which God has spoken by the mouth of all His holy prophets since the world began. 22 For Moses truly said to the fathers, The LORD your God will raise up for you a Prophet like me from your brethren. Him you shall hear in all things, whatever He says to you. 23 And it shall be that every soul who will not hear that Prophet shall be utterly destroyed from among the people.’ 24 Yes, and all the prophets, from Samuel and those who follow, as many as have spoken, have also foretold these days. 25 You are sons of the prophets, and of the covenant which God made with our fathers, saying to Abraham, And in your seed all the families of the earth shall be blessed.’ 26 To you first, God, having raised up His Servant Jesus, sent Him to bless you, in turning away every one of you from your iniquities.” (NKJV)
Acts 17:30-31
30 Truly, these times of ignorance God overlooked, but now commands all men everywhere to repent, 31 because He has appointed a day on which He will judge the world in righteousness by the Man whom He has ordained. He has given assurance of this to all by raising Him from the dead.” (NKJV)
Acts 20:18-21 18 And when they had come to him, he said to them: “You know, from the first day that I came to Asia, in what manner I always lived among you, 19 serving the Lord with all humility, with many tears and trials which happened to me by the plotting of the Jews; 20 how I kept back nothing that was helpful, but proclaimed it to you, and taught you publicly and from house to house, 21 testifying to Jews, and also to Greeks, repentance toward God and faith toward our Lord Jesus Christ. (NKJV)
Acts 26:19-20 19 “Therefore, King Agrippa, I was not disobedient to the heavenly vision, 20 but declared first to those in Damascus and in Jerusalem, and throughout all the region of Judea, and then to the Gentiles, that they should repent, turn to God, and do works befitting repentance. (NKJV)
2 Peter 3:7-9 7 But the heavens and the earth which are now preserved by the same word, are reserved for fire until the day of judgment and perdition of ungodly men. 8 But, beloved, do not forget this one thing, that with the Lord one day is as a thousand years, and a thousand years as one day. 9 The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance. (NKJV)