Hey! Current student at CMU. As the others have said above, I’m not sure where you heard that we have a stale social life, but honestly it really depends on who you hang out with. CMU has a very wide range of social levels (although we are a nerd school and proud of it). 20% of undergrads are in Greek life, which is a pretty high percentage compared to other schools. There are parties on Friday and Saturday nights (my roommate always goes to them) hosted by many of the fraternities that people go to. I think you’ll find that even people in the busiest majors (CS, ECE, architecture, etc) find time to relax over the weekend. Trust me, it gets hard here, and people want to chill out and have fun. While you will find people that seemingly study 24/7, you’ll also find others that like going out and having fun with you. It depends on who you hang out with, but you can definitely find friends who have similar social needs as yours.
If you’re uncertain about CMU’s social atmosphere, I encourage you to come visit CMU for an overnight stay! These start in the fall and continue throughout the spring, and they’re normally 2 days long. In addition, admitted students have a Sleeping Bag Weekend in April where they get to meet one another and decide if they’d like to attend CMU.
Good luck with your college apps :] Feel free to message me if you have any more questions.