"Will you come on vacation with us?"
Not this time. Thanks, though!
"Will you join us for a very uncomfortable family dinner in which we ask you invasive questions?"
I'll come over for dinner, but personal questions are off limits. Break this rule and I leave. Do you agree?
"We don't understand introversion, so why don't you want to spend all of your time with us?"
Then it's time you did. Go learn about it. Then you'll know why. And don't bring it up again until you've made a real effort to understand.
"Don't you love us?"
Yes, I do. But your behavior towards me is unpleasant for me to put up with, so I generally choose to spend my time elsewhere. Fix that and I'll be more interested in spending more time with you.
They'll either get more offensive or change for the better.
If it's the latter, you just won.
If it's not, well, they're already offending you, so nothing's really changed. "I've had my say, you've had your say, you're still engaging in behavior that I don't like, so, 'Bye.' Let me know when you've reconsidered."
I've generally found that when I've tried over and over and over and over to make polite hints or redirects and they do not change their behavior, it's either because they are completely clueless about social cues or they don't give a damn about your feelings. In either of those situations, being extremely blunt and clear is essential.
Set your boundaries frequently. And enforce them.