In classic fairy tales, the kiss makes the beast human. In Shrek , Fiona’s "true form" is revealed to be an ogress. The curse isn't "broken" by making her traditionally beautiful; it's broken by making her permanent form match the person she loves and the self she was hiding.
On the surface, Shrek is a satirical comedy about an ogre rescuing a princess, but its "deep story" lies in its subversion of traditional fairy tale archetypes to explore themes of self-acceptance and the impact of societal judgment . The Core Themes Shrek 1
Farquaad represents the rigid, exclusionary nature of traditional stories. He wants a "perfect world" free of fairy tale "creatures" , making him a symbol of societal intolerance toward those who don't fit a specific mold. In classic fairy tales, the kiss makes the beast human