"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.
I know in the US we value individualism responsibility. But the reality is many things are encouraged / discouraged, made easier / harder collectively.
Of course if you never go out of your house, you're not going to have many social interactions. But your environment and the culture you live in makes a difference too. You can quit smoking yourself clearly, but the collective push to discourage smoking has done a lot to reduce the overall use of cigarettes.
OP gave the thread a very good and valid suggestion. Treating this as a societal problem - for "society" to solve - is lazy thinking.
If you want something you've never had, you have to do something you've never done.