Personally, I think there needs to be more clarity on that. A child in its natural state displays 'selfishness', but this isn't fallen or corrupt, just immature. That selfishness functions for the child to help preserve itself. Yet, the child will still cry if mummy or daddy are sad, and still try to make drawings that make mummy and daddy happy, etc.

One of the outcomes of the Fall is that the ability for our heart (aka spirit/mind) to grow naturally and unhindered into maturity became derailed. So, instead of maturing, even as 'adults', we slip into distorted 'selfishness', twisted by fallen love.

If a child doesn't grow properly into maturity (by passing through and developing all the stages of love in unity with God - child's love, sibling love, conjugal love, parental love), then what grows? The fallen nature grows, and that is the hook that the devil uses to ensnare, undermine and drag into dark places.

The main point here is a clear distinction between what is from God (original) and what is from the Devil (fallen). Unless we are able to clearly distinguish this on all levels, then there are limits on how much we can separate from the devil and be restored to God.

Conversely, when what is original is made clear, and what is fallen is made clear, then we can advance the separation process that begins with accepting Christ, and clear out the fallen inheritance more and more from our lives, our families, and the world.

I'm not saying you're wrong; I'm saying that in today's world, where logic and reasoning are used ad infinitum by evil to confuse, mislead and enslave (i.e. Marxist ideology as one example), as a whole, humanity needs to upgrade how we understand the world so that it becomes crystal clear. This also provides the starting point for showing why Jesus is right and why we need Christ, not simply from faith or belief or feeling, but from a standpoint of logic and sensibility.

CS Lewis was a great champion in this area, for example.

On an individual level, we all have our own ways of interpreting, our own labels, and concepts that we use to navigate the world and separate truth from lies. But in a world where logic and reasoning (aka our intellect) have reached a height never before experienced by humans, the old arguments need to be shown to be right in new ways.

"Now we see but a dim reflection as in a mirror; then we shall see face to face."

BTW, you can even go further to pinpoint the key fallen nature inherited from the devil, and see how God worked hard and showed the model patterns in scripture (through the people in the Bible) to identify it, and separate from it.