Autistic headcanon: Charizard and Dragonite are close relatives. Both are orange dragons (Charizard is in the dragon egg group despite not being dragon type) with blue wing membranes, orange bellies, and horns.
Charizard has just been domesticated to reach its adult form more quickly (and be more functional as a baby, having arms and legs instead of being a little worm) and to be less powerful and unpredictable, making it safe to be owned by children, but also making it lose its dragon typing because it's no longer as powerful, wild, and virile.
Charizard is like the dog to Dragonite's wolf, being friendlier, more docile, and more aesthetically pleasing (although for Charizard it's coolness rather than cuteness).
Interestingly, before gen 8, most of Charizard's dragon moves couldn't be learned naturally, but had to be passed down via breeding with an actual dragon.