I recently got the opportunity to sit in on a friend's online psychology class where they talked about the condition and the professor made a point to say multiple times that it's a controversial diagnosis. From what I read in the past, some psychologists feel that the symptoms of DID have too much overlap with things like Borderline Personality Disorder and Schizophrenia to properly diagnose it as a separate condition.

You're totally right that if it is a real condition it is nothing like what TikTok portrays. I've seen PTSD dissociative episodes which are somewhat similar and they can get very ugly.