In my own experience, that's just not true. Facebook has facilitated lots of social interactions for me that simply would not have happened otherwise. Some examples:
- I was doing an internship in Australia for a few months. I posted a picture of the beach on Facebook, an old friend from highschool whom I hadn't talked to in years saw it, commented that I should come visit her in Melbourne. I did, and we met and caught up on life.
- A friend of mine invited me to go to a music festival with her friends. She added me to a group message on Facebook that they were using to plan logistics, etc. After the festival, we continued using the chat to plan other social activities.
- Casual acquaintances that I met once or twice invite me to parties, etc.
Can these things happen without Facebook? Technically, I suppose so. Realistically, I think they would happen less frequently. IMO there's a big difference between Messenger/Events/Groups (facilitates a lot of real interactions) vs News Feed/Profiles (stalking other people).