Why does chatgpt suck at following instructions now??

If let’s say I wanna roleplay with chatgpt as another character say a detective story and I don’t want chatgpt to improvise my character’s dialogue..why does chatgpt not understand this clear instruction?? Even if I clearly specify it chatgpt goes ahead and improvises my character’s dialogue and finishes the conversation FOR ME instead of allowing me to carry forward my character’s dialogue in my own prompts……