I grant you that selective breeding is a form of genetic modification, but it is a passive form; it's never going to have results like, for example, those horrid little day-glo-colored zebra danios.
I fully beg to differ, look at that 'natural' diversity of life on this plant that has come from natural selective breeding and natural mutations aka evolution... The 'efflorescent' gene you speak of is in fact a result of natural evolution in jellyfish and sea anemones... Man didn't make that gene, nature did... It's also flawed to infer that natural evolution won't or hasn't caused a florescent genes to appear in fish, as it has... In fact naturally florescent fish are quite common and not unique... Would that gene have ever appeared in danios naturally in due time, maybe not or possibly so that is a question no one has the answer for...
IMO never is a strong world that should be avoided in this type of discussion, as it's an inherently flawed speculation, not a fact...