Turns out giving a random amount of humanity inside of an animal may not necessarily end with the best results for the animal. If a female animal is impregnated and is relatively small, and the humanity inherited is particularly large it can easily result in the death of said animal and the baby... or if say the animal is expected to be fairly well developed as a baby, humanity's baby period could easily end in the survival of the fittest being a thing. The survival of the fittest also hadn't helped for the vast majority of babies who didn't instantly die, especially in terms of wooing others. The pheromones helped but social pressures in social creatures usually ended in some human animals that couldn't really work out with any others.
Then came babies on the human side... Turns out a woman getting fucked by an elephant or something else particularly large or with long gestation periods had a pretty serious chance of just killing the woman, and while that was somewhat rare women did tend to not have higher mortality rates from giving birth to most hybrids than normal babies. It's just depending on the type of hybrid it's possible they'd be cast out or banished as a freak, actually used more like a pet or cattle if there wasn't enough human, or sort of accepted if they were human enough. Although there tends to be a general thought that most hybrids tend to be dumber than regular humans... Not 100% true, but as most animal brains are VASTLY worse than human brains if the hybrid doesn't inherit the majority or all of their brain from their human side then there may be some... cognitive deficiencies.
As the creator had jumped a few millennia into the future they were able to see that most civilizations were at best medieval cities and the like where there were mostly regular humans and maybe a few hybrids with minor characteristics. The further out you went though the more animalistic the hybrids became. Then deep in some forests he heard there were pockets of hybrids that were practically just animals and then the Chimeras, practically 0 humanity save for the humanity gene and they managed to have mixed ancestry of so many different animals but somehow in a way that led them to be apex predators or just really good at adapting in their environment. The sort of things you may hear of in myths and shudder.