"Wouldn't that help eradicate some of our diseases that are in the gene pool?"
1. Diseases don't typically attach themselves to genes in the way you seem to be implying. True, some genes give people predispositions to certain diseases, but those are typically not the kind where a child just falls suddenly and seriously ill, there are typically warning signs. Though genetic diseases tend to be worse overall.
2. Humans have spent 150,000 years trying to remove ourselves from the 'survival of the fittest' equation. We have worked very hard to control every aspect of our environment, this includes disease.
Humans are social animals, like wolves or elephants or other apes. We evolved to rely on the survival and strength of the group in order to survive ourselves. Additionally, 'survival of the fittest' does not mean the survival of the fittest individual, it means the survival of the fittest population. This means the group best able to adapt to their surroundings and that includes managing things like disease.
"Also, if life spontaneously came into existence, why is there death?"
If the aardvark likes to read, why is there candy?
But in all seriousness, biological lifeforms, are, in essence machines. Extremely complex and naturally occurring machines, but machines nonetheless. Considering this, machine parts eventually stop working, that's what happens over time. The same goes for biological systems. Eventually, those systems break down and cannot be repaired. The most common way that happens is sheer age. That said, if there WASN'T death, that would be a point more in creationism's favor than in evolution's, because I'm pretty sure Adam and Eve weren't susceptible to death until after they were banished from the Garden of Eden.