If you think you can make deep friends when you're 40+ with 4 kids, you either don't have to work for a living and your wife does 90% of the work with children or you don't understand what deep friendship means.
Given that I nor the GP ever mentioned "deep" friendships, I probably don't understand your definition, no.
I'm simply saying there are places to meet other people 40+. Whether it becomes "deep" or not depends on both your and the recipient's dedication to maintaining such a relationship. And since you can't control the recipient, it's basically a crapshoot. But there's nothing wrong with more casual frienships.