DNA evidence is the result of eyewitness reports. An eyewitness extracts a sample, an eyewitness or witnesses maintain a chain of custody over the sample, an eyewitness runs specific tests, an eyewitness observes the result of the test and reports those results.
All evidence comes from eyewitnesses. If all eyewitness testimony is notoriously lousy then all evidence is notoriously lousy.
If we only have notoriously lousy evidence then all science which is based on evidence is notoriously lousy.
If science is notoriously lousy then the only truths we can know is truths revealed by God because any evidence we have is from notoriously lousy witnesses.
Is that what we should put in the science textbooks?
To take your logic to its conclusion, nothing we can see, observe, or test can be trusted, only what we believe God is telling us.
If that’s the reality you live in, it’s no skin off of my nose. But there’s no way to test what God is telling us, either, which sort of leaves you in a logical whirlpool.