Then I think it's fair to say that your childhood wasn't impacted in the most part by being an only child.
If you are the child of a "drug addicted criminal" that's probably rather significant in your upbringing.
Love doesn't mean "stuff." Are my parents loving because I got a pony? More loving when I got a second? Does it mean they really, really love me when I get a fancy car? To them, they probably think so. And I get that I'm massively privileged. Of course, you'd like to have a nice thing than not have it. Selfish? Yep, why wouldn't I be, I was always the star of the show, and other than when with friends didn't ever have to consider anyone other than myself. Inherently you become the only thing that matters, so to speak. Was I spoiled? Yes. Am I a brattish Verucca Salt? No. But I was flooded with experiences and stuff. Most onlys I know were. Definitely my parents overcompensating. Hell would freeze over before they ever admit it.
So yes, my childhood had loads of stuff.
But I'd have given up all the stuff, then and now, to have someone to grow up with.
Our eldest is 10yrs older than the next DC. So he was an only for many years. Constantly asking for a brother. Always longing for the company of other children. When DTwins came along he wept and wept with joy. Absolutely, there are days where he's had more than enough of them. And they each other. They fight.
But to see what they have between them, is everything I wished for as a little girl. And I hope this turns into everything I wish for as an adult.
OP is looking for stories of hope, and wobbling about what it means to be an only. She has discounted the idea of doing it alone for a second child, and I would rethink that, if it were me.
And obviously, and for the third time, experiences may vary.