I just think that while it's scientifically fascinating, and great as a fun fact to say "There's no such thing as trees actually, they're just related to various other plants" and "There's no such thing as fish, actually, they're all related to different other species" it's also useful to have a word that refers to all tall, woody plants or all gilled-vertebrates.

Either way, better Plato than Pliny.

>"There's no such thing as fish"

fun fact, your average bony fish is more closely related to us than it is to a shark

The word "fish" historically meant more or less any animal in the sea, which to my understanding included whales, seals, sea turtles, shrimp, shellfish, starfish, jellyfish, etc.

Phylogenetically, there is also a relevant group, but we call them "chordates" instead.