My understanding is that there is no Catholic requirement to believe in a Garden, two literal and off limits fruit bearing trees, or a seven-day creation. Which is good, because I don’t!
From the CCC: The account of the fall in Genesis 3 uses figurative language, but affirms a primeval event, a deed that took place at the beginning of the history of man. Revelation gives us the certainty of faith that the whole of human history is marked by the original fault freely committed by our first parents (CCC 390).
I find myself again in the position of saying, I honestly don’t know what that primeval event or deed was. I am painfully aware there is a LOT of stuff I don’t know! However, I see no reason not to believe in Original Sin as being inherited ever since. Recall, Original Sin is not an act but rather the inherited consequence of an act: the state of not being naturally in sanctifying grace.
If, whatever it was, resulted in Adam and Eve being stripped of that sanctifying grace as a permanent condition of their very nature they could not very well transmit to any subsequent offspring that which they no longer possess. That seems pretty straight forward, at least to me.
For what it is worth, I found this link to be both confusing and helpful:
newadvent.org/cathen/11312a.htm