Its God who is unable to save everyone.
If God is all powerful and its His will that none perish then there is an inability to save everyone.
I think I understand the point you are making, but this is imprecisely stated. We do not want to say straight up that God is "unable" to do anything, as if God were lower or less power in his attributes, or paint the picture of a weak or helpless God, right. The whole challenge, the whole difficulty here, is that God is allowing evil, see, and it's not that he "just can't help evil because he is so weak." If you say God is all powerful here, and thankfully you do, then we cannot define his unfulfilled desire as an "inability," because he is actually able. We should rather say that God is "unwilling" to override free will here, rather than unable.
All these theological challenges concerning this problem boil down to the old trilemma here. The Epicurean paradox presents a philosophical problem about the nature of God and the existence of evil:
1. If God is willing to prevent evil but not able, then He is not all-powerful.
2. If God is able to prevent evil but not willing, then He is not all-good (or malevolent).
3. If God is both able and willing to prevent evil, then why does evil exist?
∴ If God is neither able nor willing to prevent evil, then why call Him God?
When we question this conclusion, we do not want to question the logic that is sound. And which one of the points is the weak link, the problem here? It is not actually #1 nor #3, which are both logically sound. But #2 is the mistaken premise here. God can have good morally justifiable reasons to allow evil, and that invalidates the conclusion. But by suggesting God is unable, #1 instead is being attacked by making a weaker or less powerful god, who just has no options or ability to prevent evil, a lower kind of demigod. But the Biblical God takes full responsibility for all he creates and does not shy away from the consequences.
So when God gives his creation the power of delegation and free will, it is not because
God has to do that, but rather it is only because
God wants to do that, that is, free will is not an inability but a desire of God.