Why is crustacean a group but fish is not?

[AdamWargon]

I think Jason put it well. You might not agree with every word, but I think he makes a valid point:
(I bolded the punchline)

@jasonhernandez74

Discussions like this could become pretentious if we’re not careful. Birds may be phylogenetically within reptiles, but including them in reptiles would require a lot of changes to our practical definition of reptiles; to the point that it would be nigh impossible to have a useable definition.

There are already problems on iNaturalist due to the elimination of Class Pisces: sharks and rays which appear as “vertebrates,” because the original observer wanted to ID them as “fishes,” and the only option which has that word in it is “ray-finned fishes.” Someone else then gave the more precise ID, which is not a daughter of ray-finned fishes.

Phylogenetic pedantry only makes nature even less accessible to laypersons, which is the opposite of iNaturalist’s purpose.