The passage wont make sense without understanding what was said before.
Its about if you teach a person Salvation over an over and over, and nothing of Christ's actual teachings, then you're in effect blaspheming Christ, Paul says it implies Christ didn't accomplish what the Bible said.
A lot of people confuse the verse saying you shouldn't repent when you sin .
Christ saves . Then all thats needed is repentance .
This is about Learning, as apposed to those who've not learned .
So if you're only teaching Salvation to a group of Saved people that is wrong Paul is saying .
You have to understand the verses in a continuation of what was previously said.
Once some one is on the path to learning Gods words, and needs to get into the meat of the word
it then becomes a shame, for them to be taught Salvation , baptism and repentance .
Hebrews 6:1 Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works, and of faith toward God,
2 Of the doctrine of baptisms, and of laying on of hands, and of resurrection of the dead, and of eternal judgment.
3 And this will we do, if God permit.
4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,
That is your contrast, between those who mature in the word, who've leaned about " the good word of God, and the powers of the world to come"
And those that just teach salvation and baptism which results in " putting our Lord's sacrifice to shame. "