Back when gen 8 got leaked someone pointed out that you can generally tell a real GameFreak Pokedex from a fakemon dex by the amount of "ugly" pokemon and the number of invertebrates and inanimate objects, and I think there's a similar thing going on here- Pokemon genuinely makes an effort to make its monsters varied.
The last 15ish years have seen so much ink spilled on the Vanillish line, on gen 1 designs, etc etc, but I think it bears repeating how easy it is for a Mons game to stick to charismatic animals like mammals and birds and dinosaurs and pets. And pokemon does have that (we have, what, six cat lines? more if you count regional meowths) but it also makes sure to add, like. A crinoid. A bagworm. A bell. Creepy humanoid mushrooms, a sand castle, a big iceberg.