As someone who used to be terrible at socializing but had to learn because I'm an extrovert you've more or less summed it up.

Charisma is real and it's a factor, but it's more like having a good voice and natural presence for public speaking rather than the skills to confront stage fright, properly comport yourself on stage, and work with an audience. A person with 0 interpersonal charisma may never be making a living off socialization, but if they build skills they can easily be well liked and have plenty of friends and a partner. Meanwhile a person with a ton of charisma and no social skills is going to have a hard time keeping people around.

But yeah, practice, practice, practice. And as someone else said, benign comments are great tools. "Some weather we've been having", complimenting something someone is wearing especially if it's bold (as someone who likes bold looks "that [thing] is bold and you make it work" is great), or even "ugh this is way too [early/late/midday] for this [everyday bullshit]