Yes, this is so close to my experience too!
I sobered up at 21 after drinking my way through my teens and could not relate to adults who had already achieved things and could not even comprehend a future without alcohol. It was a big black hole as you described.
But similar to you, what i did do was look for the similarities. I remember my first few days sober, in detox, devouring the stories in the back of the Big Book and finding myself in them. Yes, that happened to me too, yes, that's how I felt, These people we like me. I finally started to see what was wrong with me and that I wasn't alone. My first AA meeting was like coming home to where I belonged and I finally had hope.
Although I couldn't imagine my future, I began on the blind faith that if I did what these smiling laughing people were doing then i could maybe have that too.
Those promises in the Big Book happened for me, but unlike you, I didn't remain vigilant and slid back into a relapse 30 years later, partially from believing the lie that maybe I had just been too young and irresponsible and drank that way because i had had nothing to lose. I quickly found out that having more to lose did nothing to help me "control" my drinking this time; it was even worse. It took me 4 and a half years to crawl back and feel fortunate to have escaped hell twice. I know too many people that didn't ever get out.