So this list provided here is a summary of the Jewish faith. It is not the steps we take to become mature as Christians and it is not for us to embrace as statements of faith. That is why he asks them to move towards perfection because perfection cannot be found in that Mosaic system and worship.
He wanted them to understand their perfection in Christ in verse 2, which he will further explained in the 10th chapter when he encouraged them avoid laying the “foundation of repentance from dead works”, this is the sacrificial system, and “of faith toward God”. Our faith is not toward God under the New Covenant, it is toward Jesus. That is why the emphasis is about Jesus and His faith at work in us.
So in this controversial place he said that “it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, and have tasted the good word of God, and the powers of the world to come, if they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame” (Hebrews 6:4-6).
This place says nothing about loosing one’s salvation after growing through a complicated process and committing the unpardonable sin. What it mentions is that “to renew them again unto repentance”