I think Irenaeus's point was thst while we are born-not sinners- with freewill, we are born into a sinful world. And, while we have the ability to choose, we will choose sin.
Not evident in the text. He clearly said we are begotten in the same captivity. He also used language in that chapter putting Adam as the federal head of mankind. Paul makes this very simple comparison in Romans 5. Romans 5 makes it clear we share the same condemnation of Adam.
Romans 5: NASB
12Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned—
13for until the Law sin was in the world, but sin is not imputed when there is no law.
14Nevertheless death reigned from Adam until Moses, even over those who had not sinned in the likeness of the offense of Adam, who is a type of Him who was to come.
15But the free gift is not like the transgression. For if by the transgression of the one the many died, much more did the grace of God and the gift by the grace of the one Man, Jesus Christ, abound to the many.
16The gift is not like
that which came through the one who sinned; for on the one hand the judgment
arose from one
transgression resulting in condemnation, but on the other hand the free gift
arose from many transgressions resulting in justification.
17For if by the transgression of the one, death reigned through the one, much more those who receive the abundance of grace and of the gift of righteousness will reign in life through the One, Jesus Christ.
18So then as through one transgression there resulted condemnation to all men, even so through one act of righteousness there resulted justification of life to all men.
19For as through the one man’s disobedience the many were made sinners, even so through the obedience of the One the many will be made righteous.
20The Law came in so that the transgression would increase; but where sin increased, grace abounded all the more,
21so that, as sin reigned in death, even so grace would reign through righteousness to eternal life through Jesus Christ our Lord.