> I have never heard “Cordyceps” pronounced with a hard C in the second position, nor any hard Cs pronounced in “Cetacea
You just need to travel more then. Millions of people pronounce it exactly like that, including me. Cetacea, Cordiceps; one character, one sound. The easy, old and reliable way to do it that worked really, really well for 200 years.
Scientific language uses basically Greek and Latin, but also other languages and names of famous people. There are specific exceptions for this cases.
Believe it or not, Squarepantsii is a latin name.
Is a collage of english names of course, BUT the final ii is not english; It cames directly from latin, so is a "neolatinism". A new name latinised (Built using latin grammar rules). Therefore should be pronounced as any other latin word. It has 13 sounds.
If we think about it, Latin is a dead language that is "so dead" that is still growing and including new words. And of course there is still people alive that speak it routinely (In the Vatican, for example).
I'm aware that this is not a popular opinion, but the anglosphere is just doing simple things much more difficult for everybody (including them), and shooting themselves in the foot. To remember the scientific names [1] is much more difficult for them than for us.
[1] (i.e Metasequoia glyptostroboides, yep, easy. Just a couple of traps here. Everything else is clear and obvious)