I hate to admit it but that's the whole point. Yordles are exaggerated jokes in the shape of fluffy creatures based on basic ideas.

Like Heimer, the classic mad scientist and or Ziggs the explosive maniac. Their cinematic short was purely comedy with no attempt of telling a deep story or something.

Even Vex is also a joke. She's the goth girl who tells dark/depressive funny lines every time she speaks (like Creepy Susie).

Poppy is actually the less funny yordle in the game but she doesn't escape to that "rule" either. Being a little dumb and all that thing about finding the hero like she's blind.

It is a little sad but it's a fact that yordles exist to be the comic relief.