"you just have to put yourself out there" is lazy thinking, you are ignoring all the underlying psychological and physilogical factors preventing people from doing it.

Making the society more welcoming works. It worked wonders for me. I moved from a country where things like meetup events are not common and groups are less welcoming to strangers. Having moved to UK, meetup events allowed me to go out and socialise because I could sign up without speaking to anyone, and go there and participate in the activity, without the pressure to socialise, it was an optional benefit. These settings allowed me to socialise with strangers that I could never do before.