I can kinda see the evil spells that does the same as the good spell but one is evil and one is good making sense in a universe of arbitrary but real good and evil, where evil exists as an ends to itself in the form of demons, evil gods, sometimes negative energy, etc. I can totally see certain spells being arbitrarily evil, even though they do what some non evil spells do (and same for spells being arbitrarily good) if the have an evil source of power or cause arbitrary evil to now exists (such as making undead or summoning demons.) and that seems to be the basic assumption that D&D spells are mostly (although I think maybe not always) built upon, and if you're playing a setting where that's not the case or certain arbitrary evil things don't count as arbitrarily evil (like undead) you need to change the spells to not be evil/good.
That said poison use being evil according to the ravages is super dumb, afaik the section on ravages is the only, or at least a very rare instance of, poison being called evil in D&D. Certainly it's not considered evil in the core books, it's evil adjacent kinda, since evil characters are often able to use it better, and paladins can't use it, but evil characters doing something that paladins won't doesn't make that thing itself evil. It's weird too, because ravages totally fit a useful niche in supernatural poisons that effect (evil) creatures that are normally immune to poisons. They'd be perfectly fine being just that, but for some reason the book had to had them stand in opposition to something that exists and make the other thing evil, because it's the BoED right?