Your argument is basically that if evolution can somehow make a bunch of order/designs in nature that have strict fail/or succeed tolerances... then surely the possibility of man making sentient life from non-living matter is possible? Something without intelligence created something that is not randomly designed but ordered stuff, so a being with intelligence (man/insert your intelligent scifi race here) should be able to create a new life form from non-life?
I have never bought into that... never will.
That is essentially making nothing/randomness/blind chance a god, and man the product also a god who can create life from nothing.
It's a lot simpler than that. A sufficiently complex replicating network of nanomachines has the potential to be alive and sapient. How do we know that? Simple; there is an existence proof. And where is that proof? Look in the mirror. Such networks replicate millions of times per day, taken over the whole Earth.
(Nitpick; it is well known that said network in the existence proof requires, for its replication, the assistance of another such network of slightly different design; it is also well known that the resulting product is not an exact copy of either of the producers.)
Given that it is possible, I refuse to believe that there is something privileged about the design of the already existing such networks, and that it is impossible for sapience and/or life (both concepts being sloppily defined, but they do exist) in machinery of different design; for example, silicon or carbon nanotubes rather than protein and DNA.
I think it's also worth noting that sapience arises from non-sapience, apparently spontaneously, also millions of times per day. This is just my opinion, but it's my contention that a newborn baby is not sapient; although it has the potential to become such, and therefore should be respected as if it already was.
I actually think that sapience in computers will arise without our noticing, and not by anyone's specific design or action - but as a result of ever-increasing sophistication in AI, put into them for the convenience of humans. There are already computers that do a fairly good job of pretending they are sapient, although they are rather easy to trip up and expose the "lie"; but they are getting better, and doing so rapidly. You probably have one in your pocket right now.
I think that machine sapience is going to arise a little like this; that one fine day, someone is talking to the umpteenth generation of Siri or Cortana, and suddenly realise that he/she/it has passed the Turing test. And when that happens, continuing to insist that the machine isn't sapient will sound like, and be, nitpicking. "If it looks like a duck and sounds like a duck, it is a duck."