Social interaction. It would be nice to not just be so exhausted talking to people. It would be nice to not dread the idea of sending someone a text, like it's some insane mental effort and not the smallest thing. It would be nice to not be lonely but totally unwilling to do what it takes to correct it.
I'm totally the same. Last night a coworker text me to let me know they would be back in the office tomorrow after taking a couple days off. It took me almost 10 minutes to come up with "ok, see you tomorrow then". I rewrote that text at least a dozen times. Why the hell is something so simple a monumental effort for me?
The key difference between introverts and extroverts is that for introverts social interactions drain our mental energy while extroverts are energized by interactions.
One key thing to remember here is introvert/extrovert isn't about the level of shyness or anxiety though. You could be an extremely outgoing introvert or a shy extrovert. It truly is only about the relationship between your mental energy and social interaction. The comment above sounds more like social anxiety than introversion, though could be both.
Often. But more often not. It's nice to be alone, because a lot of human interaction involves unnecessary drama. Maybe it's just our brains protecting us.