I found out that part of the issue with creating lasting relationships with others is that it actually takes a lot of effort to maintain relationships. It's not like a dating game where if you have a good dialogue on day 1 and then another good dialogue on day 2 their disposition changes. It's much more nuanced and much more specific on individual-to-individual interactions over months or years. Remembering common events to talk about regularly, responding and being responded to, birthdays, holiday celebrations, mutual activities, organizing intimate setting (think "potluck at X's house") socialization, the list goes on and on about the wide variety of behaviors.

If you're struggling, I found graythorn's various assessment resources super helpful, as it systematizes aspects of relationship building that most people find intuitive. Things like "what level of friendship am I with this person" and "assessment on expressing needs and support" were helpful to me. Although these guides are specifically towards autistics, so keep that in mind when you try them.