Where I struggle with this is someone can be sorrowful / feel guilt for their sin, but reject God
There is a subtle but significant difference between contrition and pride.
how disobedience in of itself can make someone worthy of an eternity in Hell
It’s not about being worthy of hell. It’s a radical choice to reject God. Mortal sin is no joke. It requires
- grave matter
- full knowledge
- deliberate consent
And to top it off, it’s not like sin is unforgivable. It’s
final impenitence that ultimately leads to damnation. It’s not something easy to explain to children, but fairly straightforward for adults.
Hell is endless, purposeless suffering
On the contrary, such suffering moves sinners to repentance and is a sign of justice fulfilled. It’s not, as it were, gratuitous. Our God is a just and merciful God, who would not allow any suffering to be without a purpose.
Sure, that suffering doesn’t benefit the damned, but there we should address the word “endless”. Their decision was made before time existed and stands outside of time, so they don’t experience the pain of damnation as we would imagine it. It’s a more “present” awareness of a consequence, which by the way they fully embrace.
Many might be sorrowful for their sins, but don’t have the will to change their lifestyle or to have the steps available to turn away from their sin.
This is very tricky. If someone is repentant, repentance is not a feeling but involves volition, that is, the will to change one’s way of life, avoid occasions of sin, and sin no more. God will take into account even the smallest step in the road of penance.