I was using vernacular language to articulate a point. I'm well aware of how evolution works, as a molecular biologist. Most people have issues with understanding the minutiae of evolution theory and the central tenets of randomness and they require primers they are familiar with to understand the broad theory. But if we are going to get into the nitty gritty, your understanding of natural selection and evolution is incorrect.

DNA was not the first success. We have evidence of a RNA world that came before, and molecular fossils of ribosomes that are protein RNA hybrids that catalyse reactions. DNA was not the first success. It was the most efficient system that nature happened upon. We know RNA is less efficient, less stable and less versatile. It is suited to its current overarching purpose, intermediation between DNA an protein. But it was a necessary step. At DNA, natural selection ceased making direct alternations and enveloped epigenetics instead. Indicating heavily that there is little better than DNA and the only gains to be made are intrinsically altering the current system.

Survival of the fittest does not mean survival of the empirically best organism it means survival of the organism most suited to its current selective pressures ie the organism with most fitness. I never claimed otherwise. We aren't talking about organisms that have to worry about rocks falling on their head. A change as fundamental as DNA takes fitness to the marginal gains level of molecular biology. Nature will streamline the process of molecular cascades to use the least energy possible, this is a universal facet of evolution. On the rare occasion it doesn't happen is because there is increased benefit of using a more energy intensive system. Most organisms live in a perpetual state of scarcity of resources and cannot afford to be wasteful. This is pertinent on a single celled level where any change in molecular structure will happen. Complex multicellular life has jumped the shark at this point. We are too far gone to ever see a change on that front with something as basic as DNA.

But single celled orgsnisms, who still deal with the extreme marginal gains of nutrient scarcity that had existed since the primordial soup operate on that level with the capability of mass molecular change in a few generations. And yet. Nothing has changed from a basic nucleic acid standpoint in billions of years. Evolution is not an isolated microcosm. Mutations don't just crop up once, die off and that's that. The same mutation will crop up multiple times at random. If it provides fitness, on a level as universally used as nucleic acid, it will stick. The other option is that DNA is as storage efficient ad it can be. Which is the far greater likelihood given the rest of the explosion in diversity among orgsnisms and the fact that multiple other systems have existed before which were less efficient. Nature never stops, that's true. But if it can't get better, it can't. The notion thsy amazing ideas died with a single 'unlucky' organism is scientifically illiterate. Mutations don't just occur once. They reoccur again and again. If they provide increased fitness such as reduced energy consumption or more efficient gene transcription they will stick at some point. Convergent evolution of traits demonstrates this. The same idea is happened upon many times independently by nature. It's not unreasonable to expect this trend to occur at every level and indeed it does down to a molecular perspective.

Trying to argue that something better may have existed but died off is possible but again, scientifically illiterate. You can use that argument to suggest anything at all with no basis whatsoever other than conjecture. We know what we can measure and we know what steps nature went through that lead to the creation of DNA. It's so tremendously unlikely that an organism had something better than DNA but didn't survive. The advantages to survival are far too great from the increased potential variability, reduced energy consumption and metabolic streamlining.

Luck is not a concept the universe deals with. It doesn't exist. It's a figment of human desire to attribute fate to anything other than pure randomesness.

I disagree on your assertion that biology is limited to our state of knowledge for the reasons I outlined. Chemical biology is a known quantity and the laws of physics apply to the entire universe. Non Carbon based life is a dream for people who don't understand how molecular biology works. There is no other atom that offers the same stability and variability as carbon at temperatures and pressures reasonable for biological catalysis. There just isn't. You can try and argue that there is but again, it's scientifically illiterate and a pointless argument unless you can identify specific examples.

If something as fundamental as a new element exists that offers better variability and stability than carbon, we were unaware of, it would require us to rethink our entire understanding of science in a way I don't think people fully comprehend. We know we aren't wrong in entirity. There isn't room for more small mass elements in our current model, which we use to determine everything from how molecules look to how they hone together to how to keep planes in the sky. We understand how the entire periodic table fits together. If another element appears in the middle, we are wrong on almost everything. This is why the fantastical 'well maybe there's something else' ideas don't hold weight. There's virtually no room for that idea to exist without planes falling from the sky because we are completely wrong about chemistry and physics. And within that framework, DNA is the best we know of, that nature has happened upon. Anything better is virtually impossible. Regardless of how alien the life is. If it did exist it wouldn't even use anything vaguely resembling DNA. It would have to be a molecule we haven't even considered. And there are only so many ways to arrange atoms in a small molecule. And believe me, we have tried a lot of them which are chemically and biologically viable. Not all. But many, as people search for what might be an alternative. And they almost all arrive at the conclusion that anything else just isn't worth it.