You can say “I’m schizophrenic”.
It would be dumb if you could say “I’m schizophrenic” without experiencing the schizophrenia.
Because I feel being able to say you’re schizophrenic is empowering in some contexts. But you shouldn’t be able to have this power unless you’ve suffered due to the illness in mind.
Seems obvious but when I’m having a bad day or a bad moment I say “what did you expect from this illness!? Rainbows and unicorns 24/7??”