That doesn't help with the day-to-day of things, but it does contribute to an overall happiness which I do not think the medication alone would offer me.
But if you employ a tonne of ADHD coping mechanisms and they work for you it'll improve things a decent amount.
I haven't tried CBT but it's a recommend approach. I'm trying (painfully slowly because it's not super interesting) to teach myself DBT to help with it too.
Dx is only strictly required to get Rx but an additional benefit is they do a differential diagnosis so they make sure it isn't down to depression, anxiety, sleep problems, trauma etc. All of which can cause some of the same symptoms.
There are a tonne of people who get diagnosed with depression and anxiety and the recommended treatments just don't work that well for them. Then they get diagnosed with ADHD, everything falls into place and they can get their life together so they're not anxious they're going to constantly screw things up nor depressed from shit life syndrome and the depression and anxiety go away.
I was wondering if I had ADHD; in all the online tests I score in the ADHD or borderline range. But it's just symptoms of my anxiety which is particularly bad at the moment. If I'd done the tests a year ago, the result would have been completely different.
An analogy you might be experienced with: imagine you're a product manager and you want to make a customer service person in your company twice as efficient as they are today. If you ask the CS person what you should work on for them, they might be able to give you some direction, but they don't know the full range of possible things that you can do for them. E.g. they might think "Well, I've got to type emails to customers so it would be useful for me to have a new support ticket load on my screen as soon as I'm finished with the last one." But you -- an expert -- might say "We can actually auto reply to some of these emails for you using a canned template!"
Self-diagnosing, and in particular self-diagnosing mental health and neuroatypicality issues, is a hard ask.
With that said, medication is also quite helpful. In my experience it provided a quick and independent support to my feeling better and productive. I found them critical when the controls I had built for myself proved insufficient or had collapsed. For example, when I moved from an office job to remote work I found the change and the lack of societal pressure to be focused on work left me in disarray. Medication helped me stand myself back up and find the routines and structures that worked in the new environment. As I built these support structures up I found the need for medication was reduced and stopped taking medication for many years. Years later, after a cross-country move which came with the loss of local friends and community I found it necessary to restart. I prefer to not take medication unnecessarily so one day I may be at the point where I stop taking them again, but I'm not there yet.
My advice would be to try medication if your gut says you need it but if you already feel fairly happy and productive then it may not be necessary.