I think this is a problem with the “cynically use” part more-so than the “self-diagnosis” part. I know you didn’t say all self-diagnosis was bad, but I wanted to share a bit about mine. My self-diagnosis helped me:

• come to terms with using sensory aids in public
• connect with other people who struggle with alexithymia
• explain a lot of social alienation and confusion from my childhood
• give my therapist better direction for tools to teach me

I would have been happy to get a formal diagnosis, but the only person who does adult autism diagnoses within a 2 hour drive of me charges $2k for the privilege and doesn’t accept insurance. All the resources around here are for autistic children. On one hand, I was happy that my son had so many resources. On the other, it makes me wish that I’d had this revelation a lot sooner.