Earlier quoted context omitted.
I make new friends of all ages all the time. At church. It does provide "proximity; repeated, unplanned interactions; and a setting that encourages people to let their guard down and confide in each other". And not by coincidence. One of the major goals of church is to help people form healthy and significant relationships (that is, friendships).
I grew up in a church and this is basically the only thing I miss. In fact it just makes me angry when I think back -- here we have a warm community in which that friendship and companionship are available only on the condition that you alter your cognition and beliefs to conform to a very precise code. Some serious strings-attached.
For example literally being in a college, being in a mess in the military, being in a sports team.