The only people that truly don't fear real death are atheists that have made peace with that fact.
I am a atheist that has not out grown a fear of death, but I can't relate to anyone I know because they all say the same as you, "you will eventually out grow that fear", then I ask what if I am right and when we die we are forever gone and there is no afterlife? They say "Well that is unlikely, there is something else out there" So everyone I know doesn't fear death, because they think they will never truly die anyway.
Like I said, the only people on earth that really do not fear death are a small amount of the atheist population that have come to accept death as inevitable. But what I think is that if all of humanity was atheist, we would be pouring billions in immortality research.
You don't truly want to live forever, and lose everyone you know and will ever know. If everyone lives forever, then children will never grow.
Once you truly accept that change in not only inevitable, but extremely desirable, the fear of death is greatly diminished.