I'm going to guess that your partner (a woman?) is now...in her 30s? and now a cellar dweller?
I'd guess the current relationship partner expects and asks very little of your ex. The two of them are satisfied to behave like aging adolescents, hanging out in Mommy's basement - and probably on the road to drinking again. I mean if you really want to change your life, you don't set yourself up so it's easy to fail and there are no consequences. Do you?
Your ex found someone who will accept her (or his) addiction. That's not so much rejecting you as taking the easy way out.