When & why is it not wise to seek out help?

This is not a post trying to alarm you, but it is something that reality may throw at you that will hit hard.

I had vaguely brought up the possibility of neurodivergence to a psych, and they told me: "Okay so you probably are, but I'm not going to diagnose you because it'll make it more difficult for you to get care / to be medically taken seriously."

Was recently talking online to a friend who was diagnosed at 14, and both their parent & their psych agreed not to add it to my medical records because it could "ruin [their] life."

I have been seeking out help with my issues all my life, and have one current diagnosis (ADHD-PI) that is so severe that I nearly destroyed my life several times when I was off meds. I am not "seeking" an autism diagnosis, but I'd love to have helpful resources.

Let me be clear: doctors already dismiss my ADHD diagnosis or straight-up let me know that "you probably don't have ADHD" in so many words. I have yet to be taken seriously regarding it, and it has harmed me immensely and put me off from seeking therapy or support for it.

Autism? Holy shit, forget it. Not a single medical professional I've seen wants to even touch that.

This feels like fucking "Nightmare Mode". Mask until you die. Ultimate stigma.

Why is it near impossible to find help with adult ADHD / autism / other neurodivergent diagnosis? What the fuck is going on? And, more importantly, what can we do about this?