If you roleplay or do fanfic or write any story—original or some fanfic of an already existing story—the dialogue sounds awful, and that’s true for every AI: ChatGPT, Claude, Grok, etc. Mainly, the dialogue is unbelievably repetitive, and then characters either have an overreaction to something or an underreaction to something. The dialogue sounds truly, truly awful. No one really has a distinct personality; they all sound the same, repeat the same lines, and the dialogue is cringelord-tier. It doesn’t sound like real, actual people talking.
LLMs build plausible-sounding texts. They don’t have to be correct or even good.
Think of it this way: If you take all of the dialogue in digital and print media (include forum flame wars, cheap romance novels, and fanfics) then try to get an average out of that - what do you get?