We may understand a lot, but nowhere near enough to be able to confidently edit DNA, and know that it won't causes a ton of unforeseen issues down the line.
We don't know what we don't know ~ that is, as much as we like to believe that we understand a lot about DNA and how it works, odd things pop up all the time that prove us wrong. I dare say that there are far deeper mysteries about DNA that we have no current understanding of.
> Nature does not ‘know how’ to make it work 99.99% of the time. Nature very frequently aborts pregnancy’s when any number of things go wrong. Getting all the way to birth is a huge checksum that validates the majority of critical DNA.
This is merely an example of nature getting it right ~ abort if there are serious issues.
> Which gets it the larger point. Evolution focuses more on species propagation than individuals.
It is about both ~ the individual matters most ~ species propagation doesn't even register in importance to a majority of individuals. Having children does. They're subtly different ideas.