What is your evidence of genetics? Unless you are a biochemist and have run experiments yourself, it will boil down to “somebody told me/I have read it in a book”. So your evidence boils down to a chain of narration. Which narrators you trust or distrust is a subjective matter.

Genetics are a great example though. Modern genetics are often perceived to start with the work of Mendel in the 19th century. Imagine instead of being taught about genetics in school and maybe later in university, you would have lived in the 17th century. Would you have rejected the concept of genes as “fairy tale” because there was no evidence you deemed credible available?

What about atomic models? Would you have considered them to be “fairy tales” prior to the developments of the late 19th and early 20th century? What about how atom models changed? Would you mock Nils Bohr because his atomic model became partly obsolete with the work of Heisenberg? Did you do any of the experiments which lead to the developments of atomic models yourself?

So in practice the only scientific approach is to say: “I have neither evidence that convinces me for or against it, therefore i don’t know”. Saying something is false or does not exist because you don’t see evidence for it, is a matter of faith, rather than a matter of science.