>>26986693See
>>26986993.
Take Bellsprout and Trevenant's case. Bellsprout is exotic enough to most people that it only needs eyes and to walk funny. Trevenant has more effort put to it in theory but haunted trees with faces are a very tired idea. The key is to make something you don't see every day even if it's not that creative in theory, like a fuzzy yellow spider or a ball with magnets. Phantumb is better because even though it's just a ghost with a treestump at least you never see that regularly.
Most importantly, if you're basing it on something that is exotic enough that looks good already then DON'T FUCK WITH IT too much. Charizard is just an orange dragon with the tailtip on fire and that's why it's so popular. Feraligatr is a blue alligator that can walk, what more could you want?
Look, take this fungus. You could make it a bit cartoony and it would already be interesting to most people. Now combine it with a spider. There's a pokémon that looks cool and it didn't need much thinking!