There is no problem actually, but there 1.18 billion Protestants all across the globe who have not read the Book of Enoch or would even give any credence to it, so it shouldn’t be a surprise that people haven’t heard of gene-splicing from Heaven.
Well, it wasn't exactly from Heaven. These were fallen angels wanting to change their DNA to be able to copulate with human women. I understand it isn't canon but everyone knew about in NT times. It was available and well read.