The diagnosis itself isn't important per se. The important thing is becoming aware that you are autistic, thus opening up a whole community of people who have had similar struggles to yours.

There are many aspects of an autistic's life that a non-autistic simply cannot comprehend, and so it's unlikely that anyone but another autistic would have figured out ways to deal with them, and how to better fit into the neurotypical world.

I also guarantee that you have many behavioral quirks and ways of thinking that are VASTLY different from the majority, and that you're unaware of them because you haven't yet recognized the difference from a "normal" person. Learning these things makes other peoples behaviors and reactions to you a lot less baffling, and is the first step in improving relationships.

The sheer volume of literature and people that become areas of interest and information once you are aware of your autism is what makes a diagnosis (self or professional) worthwhile.