Do you read the Bible that came before the gospels? Are you aware of the covenant relationship God had with Israel?
Let us look at your verses, since this is what guides us.
Mark 1:14-15
Now after John was arrested, Jesus came into Galilee, proclaiming the gospel of God, and saying, “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.”
For whom was the time fulfilled? Answer: The chosen people of God. The people of the promise. These person's were called to repent and believe. This was not for all humanity.
Luke 24:44-48
Then he said to them, “These are my words that I spoke to you while I was still with you, that everything written about me in the Law of Moses and the Prophets and the Psalms must be fulfilled.” Then he opened their minds to understand the Scriptures, and said to them, “Thus it is written, that the Christ should suffer and on the third day rise from the dead, and that repentance and forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem. You are witnesses of these things.
Here we see that the elect and chosen from all nations are to be called to repentance. 1 John 1:9 tells us that God is faithful to forgive us.
Acts 2:37-38 has already been addressed.
Acts 2:37-38
Now when they heard this they were cut to the heart, and said to Peter and the rest of the apostles, “Brothers, what shall we do?” And Peter said to them, “Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit.
Notice what God did first. Do you see it? I bolded it for you so you can clearly see what comes first.
Finally...
Acts 3:16-21
And his name—by faith in his name—has made this man strong whom you see and know, and the faith that is through Jesus has given the man this perfect health in the presence of you all. “And now, brothers, I know that you acted in ignorance, as did also your rulers. But what God foretold by the mouth of all the prophets, that his Christ would suffer, he thus fulfilled. Repent therefore, and turn back, that your sins may be blotted out, that times of refreshing may come from the presence of the Lord, and that he may send the Christ appointed for you, Jesus, whom heaven must receive until the time for restoring all the things about which God spoke by the mouth of his holy prophets long ago.
Notice the emphasis on faith.
Notice Peter calls them brothers. These are not pagans. God has cut them to the heart. Thus, they will respond in repentance.
Are you still unable to see that God first makes people alive before they can respond in repentance? The very passages you chose actually show you your error. Now, will you continue to deny God the glory and honor he deserves as the one who drags rebellious people to Himself?