I'm A Banana
Potassium-Rich
*Shrugs shoulders* Maybe I am just the odd one out. But I have always found it is the mechanics and artwork that inspired me not the fluff.
Whenever I made up encounters or the way monsters worked, I never once look at the fluff the monster has, since well it is my world, so the monsters will work my way.
The easy litmus test is this:
Did you play 3e? Did you use the phantom fungus, ever?
The mechanics are cool on that one. It's a low-level threat that is invisible and also a plant, which means that it's good at surviving what the PC's can dish out. It automatically negates the "magic missile every round" strategy, and also the "flank him and then stab him" strategy, which are the basic combat strategies for low-level characters.
I mean, if you didn't use it, maybe you thought the artwork was dumb? That's a pretty subjective thing, I guess, so I won't debate it.

By the mechanics, the Phantom Fungus should have been in everyone's game at the mid-single-digits. Very cool encounter potential.
But it didn't tell a DM how to use it very well outside of the statblock.
Most commentary I've heard agrees that it's a pretty lousy monster -- the flumph of 3e. I'd be excited to learn that someone beat the odds on this one.

Alternately, substitute the ythrak, the digester, or, heck, even the destrachan (and I'm being generous on that one, because their fluff is perhaps the best out of the group).