Unlike the younger Earth, we have a thick atmosphere full of millions of chemicals that keep the oxygen we breath in, and protects us from space junk from colliding with us. Also, the earth we know today isn't insanely hot. The younger Earth had a surface temperature that was not possible for sustaining life. But now, it's just right!
Also, we have vast salty oceans. The younger Earth had a kind of ocean, but these were made of molten metals and other rocks.
I hope this helps!! :)
