To me a formal diagnosis gives you access to try medication if you want. Even if you’re not interested or ready for medication, a diagnosis (formal or not) can make it easier to find strategies and tools that work for you. Lots of general productivity advice just don’t work for ND folks, and looking for specialized tips makes a big difference.
To me having and accepting my diagnosis helped me accept me as I am and stop thinking I’ll magically be better next week or next month or next year. I now put systems in place to help me with my weaker points and that’s OK.