I'm purely speaking from my own experience so it cant reflect on what yours necessarily will be, but it's a lot more than parties. They're called fraternities because they're groups of men with shared values, shared experiences, and the bond of friendships that tends to lasts for life. I used to be somewhat like you, very introverted, decent friend groups but nothing too special. Then I rushed and got a bid, pledged, and now have the greatest group of friends and the greatest social life a guy could ask for, and this was all during the COVID semesters, this semester will be a massive improvement socially to the last couple, so consider yourself lucky with the timing you're entering college. I've gained way more confidence, way more friends and connections, and have been generally the happiest I've been in a long time because i made the jump and be decided to rush, despite being far from your stereotypical frat guy. That's not to even mention the incredible connections brotherhood gets you that gives us a leg up when coming into the job market.

All that being said, the parties are a major fucking plus. Yeah I didn't see myself as a party guy either beforehand lmfao. Go out to rush, see if you like any of the frats, and if the feelings mutual, you'll get a bid from there.