No... That's just plain silly.
The fact other
scientists in a multi-billion
dollar gil corporation were examining and experimenting on an alien creature for the same
profit driven project they were paid to do, doesn't "de-value" Sephiroth's revelation of his origins, his "other-ness" or his status as Jenova's "child." It would be quite unusual to discover no other scientists were employed with Shinra, or capable of formulating their own theories on how to replicate a Cetra when the company had the resources and motivation to go all in on a large scale project as that.
Hell, fans were theorizing on the possibility of failed "Cetra" prototypes of Sephiroth since 1998, and it never was seen as "de-valuing" his legacy or status as the ultimate SOLDIER.
You really think Shinra and it's science department would successfully genetically map and hybridize a human and unknown alien species
on the first try? No, biology of that level would need trial and error. And in the end, it changes nothing. Because Sephiroth was the one above all others.
Sephiroth being removed from humanity wasn't merely based on his biology. It stemmed more from the fact he was
peerless as a SOLDIER and a human. No mortal came close to ever matching his power while he was with Shinra. And while he grew up, he had no friends or children to bond or identify with. He grew up alone as a special
project being told he was superior to all other humans.
The existence of Genesis and Angeal as weaker, failed attempts at creating a being like Sephiroth changes nothing. Because they were not only inferior, they also got to live normal, happy lives. They got to join SOLDIER by choice. They had a childhood. They knew love and affection. Genesis And Angeal may have been SOLDIER 1st class like him, but they are not even close to his equal, nor do they share his experience.
No, what pissed people off about Crisis Core, were two things.
Genesis dropping in at the Mt. Nibel Reactor and giving up the secret on Jenova, and Genesis having a huge ass black-wing like a copy-cat.
Oh, and random Gackt self-insertion.
That's what rubbed fans wrong.