I’m not sure what your point is. Pluto was never considered a planet by the classical definition used in Shakespeare’s time, mostly because it hadn’t been discovered. But of course, by the classical definition Earth isn’t a planet either.
Actually it turns out not all spiders are venomous
Maybe we could start a thread about animals recently found not to be venomous.
And by the modern definition too, Earth has not cleared its neighbourhood either.
Regarding the distinction between “poisonous” and “venomous”: how long have people been making the distinction of “poisonous means it secretes toxins, venomous means it injects toxins”? It seems like it should be a useful distinction, but I’m not convinced that actually makes it incorrect to use terminology like “poisonous snake.”