I could be wrong about this. Not that Taxonomy is not Reality. I'm super-ultra-confident about that. I could be wrong when I say that it seems a lot of people don't seem to recognize that our choice to categorize things in a certain way does not make that categorization implicit.
If I choose to classify my social circle by their hair color, it does not mean that all brunettes will share certain personality traits. My classification does not eliminate their real variety.
It seems really obvious doesn't it? Yet many witches seem to have no problem classifying a wide variety of things as "water" and expecting them all to be good for the same watery things.
This isn't about my frustration with the classical elements though. Well, not entirely. It's about language. It's about classification, and how classification doesn't encompass everything that is, only the things you have observed.
For example: One of the most common classifications in modern witchcraft is the four elements. It is a convenient taxonomy. It has a small number of buckets and it is fairly simple to place things in one bucket or another. But just because we choose this taxonomy, doesn't mean that the taxonomy is a fundamental underpinning of reality. It's a set of categories we decided upon. Reality is rarely that tidy.
For instance: water (like what you drink) and motor oil are both liquid substances with some lubricating properties and easily fall into the element of water. Great. But their properties are dissimilar in more ways, and more important ways, than they are similar. But they're still both water.
We could come up with examples all night. Just because we have a taxonomy that could apply, doesn't mean that the taxonomy is useful.
And back to my actual point: Our taxonomies are things we made up. Hopefully we made them up based on careful observation, but they are still classifications that we invented. And because we invented them we only have to use them so long as they continue serving us. The universe doesn't obey the lines we've created, and it is foolish to spend energy on mental gymnastics to make something fit into a specific classification.
One of the keys of taxonomies that I haven't mentioned, because it is the thing that we suck at in the communities I've been a part of, is that they grow. As we discover new things, our classification evolves to make places for those things. Yeah, we are not good at this part. Over 2000 years but there are still only four elements? In 2000 years and we've never learned or discovered something that caused our taxonomy to grow meaningfully? Nope, electricity is definitely fire, so are photons.