From my perspective, I think most people want to be socially isolated, or at the very least, never change their social bubble. After completing school, I didn't want to be lonely when living in the working world. So I bought a few books on socializing, picked up swing dance, went to meetups, took adult education classes and volunteered in the US election. After 16 months of continuous practice, I have made 0 friends.…
Just show an interest in people, without being creepy. Respect boundaries but show you are a good listener and ask questions that show that you have listened and do care. Rather than shotgun everyone, just be friendly and interested and concentrate on developing relationships with people that appear interested in you.
It is also important to not rush things. If you perceive a connection with someone - don't ask them around to your house for drinks immediately, but develop the relationship for a few more meetings before taking it to the next level (I mean this from a platonic point of view).
Also consider your appearance and personal hygiene. Are you dressed about the same as everyone else? Try to be better dressed than average without being extreme. Have you too much deodorant? Are you freshly showered? Do you have bad breath?
Try to ask a family member or honest friend the tough questions about yourself.