I don't know. The idea is old and looks solid but the more I think about it the more I don't buy it; people have less good friends. Many people are estranged from family. Many people barely say hello to their neighbors. Maybe we should expend our limited energy on the people we do know instead of strangers waiting for the bus.
For me starting something with a complete stranger is draining; I need to overcome a psychological barrier (that's probably there for a good reason); so the risk is there. The reward ? I'm not sure. Some interactions could be fun, many could be boring and draining. Sure I could get better at this skill of talking to strangers with lots of struggle but the end game isn't really clear, it's not gonna flip my personality into a charismatic stranger lover. I could use the time to quietly stare at space or call my mom instead.
I think you're missing the part where interacting with strangers is also working the general socialization muscle. If you find yourself being more social in general, and give yourself the time to recharge, then you'll be better equipped to engage with those closest to you. You may even get lucky and add someone else to that circle