Irenaeus does not claim that man can be saved without divine aid.
What he says, is that men will be held accountable by God for the uses to which they put their free will.
The Bible is quite clear on two things: that God is sovereign, and tht we are responsible. What's in the middle is a mystery.
I believe it would be simplier if we simply cut to the chase; where do you believe your faith come from? Do you believe you generate your faith or do you believe God gives you faith?
The scriptures states that God brings us to repentence:
2Ti 2:25 with gentleness correcting those who are in opposition, if perhaps God may grant them repentance leading to the knowledge of the truth,
Faith comes to us through hearing the word of God. And we are told that not all men have received faith.
2Th 3:2 and that we will be rescued from perverse and evil men; for not all have faith.
And we receive the wisdom of God.
Eph 1:17 that the God of our Lord Jesus Christ, the Father of glory, may give to you a spirit of wisdom and of revelation in the knowledge of Him.
If God gives us faith, repentance, and wisdom, then what is left? And we know that God does not grant faith, repentance and wisdom to everyone.
As far as God is sovereign and that we are responsible-it really isn't a mystery. We are in bondage until God opens our ears and eyes to see the things that are of God. It is because of Christ that we can say that we once were blind but now we see.