Yeah, that's a conundrum to be sure. It sort of feels logical that if you weren't successful at making friends during the prime years for that (youth, young adulthood) then there's not much reason to believe you'll have more success in the more difficult years.
For example, I sort of maintain 2 friend tiers. Tier 1 friends are the "friends for life" I've made along the way. We all maintain a chatter and we may not see each other frequently but we do when the opportunity arrises and we just pick it up, totally natural, etc. This group is pretty much immutable at this point besides the death of friends along the way to our own death.
Tier 2 friends are more like "friends of convenience". These types will drop in and out of your life for a variety of reasons. They're the kinds of people that are your wife's mom friends' husbands, work friends, neighbors, etc. You socialize on your better behavior and although you enjoy each others company, you're usually just meeting because of some convenience, like a BBQ or child's/their birthday, community event or w/e.
Because the truth is this - most guys, by the time they either have created a family or are looking to create one, aren't looking for new friends. I'm not interested in trying to build new, deep relationships with other guys at this point. I have the family I've built, my core friends that I have real bonds with, and my acquaintances that we enjoy each other's company and would attend each others's funeral, but wouldn't speak at it.
I think joining an organization is your best bet. Getting involved in something and becoming an active member in it. You need something that forms a common bond with other people looking for that sort of thing.