For me, the main issue with cloning is that it inherently assumes that the cloned organism is way better than any potential organism you could get the ol' fashioned way. Like eg. people cloning their old pets are literally saying that their old pet was perfect and any other puppy/kitty couldn't match them.
Though it's a nice strategy to get a bunch of soldiers quickly
You didn't factor recombination. Nobody ever receives any of their parents' exact chromosomes, except the sex chromosomes from dad - each pair shuffles up the equivalent DNA between the 2 chromosomes, resulting in 2 chromosomes that are each a mix of both of that parent's chromosomes of that pair, one of which is passed on to the child for each pair for each parent.
I had to check the math and I was surprised that 2^42 is “only” 4.4 trillion. Thought it would be a lot greater like there are less atoms in the universe similar to the uniqueness of a shuffled deck of cards.
I figured this out while thinking about Red Dwarf. Canonically, Lister is his own father. How can his DNA remain stable across all the time loops if he's saturated his own ancestry with himself? This is the answer. It was a 1 in 2^42 chance the first time, but after that, the time loop preserves the coincidence and Lister ends up his own clone every time. He gets all his own DNA from himself every time, and then he just has to get the same DNA from his mum every time. The science is sound. It's tremendously unlikely, but in the infinity of the universe it had to happen eventually, assuming an infinite supply of time travellers banging their own mums.
You can also apply this logic to Futurama, Star Trek, and any other science fiction show with a grandfather paradox.