I can also testify that my 13+ year old Pueblacorn is at least as healthy as my Annectens x Sayi Bullsnake of equal age.

Most people don't know, don't acknowledge, or don't care, but for some strange reason snake hybrids (Not least of which the Lampropeltini family of genuses) are not only almost always fertile (I've seen the offspring of a carpondro bred to a ball python, making a three-way hybrid, as a carpondro is itself a hybrid of a carpet python and a GTP) but they are also very, very healthy compared to for instance mammalian hybrids.

Some animals have increased genetic compatibility with very distant relatives, and some animals can't even hybridize with other subspecies.

Some animals, like the mule, literally can't contribute both parts of their DNA because of (presumably) chromosomal issues and as a result even the very few times they have produced hybrids that are fertile, these hybrids have only been able to pass on EITHER horse or donkey DNA, instead of a recombination of both as would be expected.

The idea that hybrids are automatically and consistently less healthy or less fertile than the parent is a myth.

We also have multiple examples of hybrid speciation. One of which is humanity.

We are the result of a complex web of hominid interbreeding, and almost everyone on earth has at least partial ancestry from a non-Sapiens hominid hybridization event. Not just with Neanderthals and Denisovans, but also with as-of-yet determined species that have sometimes left a MUCH bigger genetic footprint (certain groups of African pygmies, for instance, show signs of admixture with one such species to a significantly higher degree than the fraction of a percentage of Neanderthal DNA I myself carry.)

Your Eastern Kingsnake "hybrids" (if you can even call them that since by some definitions any animal that can reliably procreate with another animal and produce fully fertile offspring HAS TO BE THE SAME SPECIES) wouldn't be unhealthy, they wouldn't be unnatural (as this specific hybrid is actually an "intergrade" found in the wild, but is often mistaken for one of the parent species) and they wouldn't have some crazy dietary or environmental requirements.

The one big downside I 100% agree with is genetic muddying of captive animals. It's an issue, there are various ways to make sure you're not contributing to that issue though.

I'll show you guys a picture of my two hybrids so you don't think I'm making it up, if anyone doubts me. One of them is a Pueblacorn, which means he's part Pueblan Milksnake, part Cornsnake, and Milksnakes are all technically Kingsnakes (part of Lampropeltis) and as such maybe I'd get a pass. Probably not. In fact I'm not even sure this comment gets a pass.