We misunderstand the verse because we do not think about it with the mind of Christ within the kingdom of God.
Btw: The Roman church invented veinal sins: sins ranked by offense. They could charge more to those who committed them.
Any way, the sin of blaspheming the Holy Spirit cannot be forgiven because He is the arbiter of truth. This truth comes from the Son. The Son received this truth from the Father. So, the Spirit ministers the standard of truth as decreed from the throne of God. The Spirit only ministers what He receives so we are assured there is a 1 to 1 correlation between what God decrees and what the Spirit says.
One thing the Spirit ministers is conviction of sin: assurance that substandard behavior misses the mark of the standard of God. If a person holds to the idea that the Spirit is not correct or that He is wrong then the person refuses to be convicted of his sin. Consequently there is no possible way for repentance and no forgiveness. In the same way one cannot say they love the Father and reject the Son. If they do, they lie, because the Son represents the Father in all things. These are kingly principles of representation.
Now, theft, trauma, abuse, lying, etc. can all be forgiven without repentance from the offender. We can simply forgive and release the offender from any debt they owe us. Likewise, if we are the offender, God will also forgive our sins upon confession perhaps with no interaction with the one we offended. But, God will not release one from blaspheming the Holy Spirit BECAUSE HE IS THE ONE THROUGH WHICH CONVICTION OF SIN AND GODLY REPENTANCE COMES. God will not circumnavigate His prescribed order: the Spirit convicts and the man repents. He will not act in the stead of the Holy Spirit. So, the sin of blaspheming the Spirit will remain for eternity UNLESS the man repents.
The plainest example of this is Paul who persecuted the church and called the work of the Lord evil. We know he did this while the Spirit was ministering conviction “Why do you kick against the goad?”. It was not until Paul received conviction and repented that he was restored by the Lord.