I really don't like the Shrek films. I find the character designs really ugly - not talking about the ogres but the human characters. I find Dreamworks animation style pretty charmless in general, though Puss in Boots 2 was an exception.

Dreamworks movies feel kinda cynical to me. And the formula of celebrity voice actors, instantly dated pop culture references, winking "gags for the adults", and random insertion of a popular songs is annoying to me. I'm just not into them. The How to Train Your Dragon ones stand out as being better than the rest and, as I say, Puss in Boots 2 is also good.

I respect all of those who are into them! I come in peace. I'm just trying to answer the question of why some might not like them.