> It’s a very young field

https://en.wikipedia.org/wiki/Epigenetics#Definitions

That depends on the definition. But, if we use the modern definition, it emerged (or re-emerged) in the 1990s. It's not old, indeed, but I also would no longer call it "very young". It's soon 40 years in the modern definition, and much older if we include prior discussions.

A young field can be immature, regardless of age.

E.g., I would regard computer science as a very young field.