Well, it's an argument. I certainly don't know to call it good, and it doesn't match my experiences in any way. Perhaps you have access to a hidden cache of deep teens that I, as an old, wouldn't understand.
To me "richer" implies more complex, with more subtle features - not "deeper" in any intellectual sense.
As an older person, I really find it difficult to care if a particular friend didn't like an Instagram pic I posted. I really don't care how quickly they liked it and I don't even know which of my Facebook friends don't follow me on Instagram. They are all social interactions that add complexity and richness to the experience, and I don't pay attention to any of them.
To me richer means conversations and experiences. I love a good discussion about technology, politics, brewing, and many other subjects. Or just about life in general.
I also like experiences such as a good hike, bike, camping trip, eating out, etc...
Sending a friend a pic or even interacting on facebook doesn't really do much to further the friendship.
> Are you seriously doubting the premise that people mature as they get older?
I do. Biologically? Maybe. Mentally? I doubt it a lot. I know lots of people of all ages who use Facebook for the most vapid, shallow, and empty experiences. Socially or not.
I don't mean this as dismissively as it may sound, but it seems possible you'll figure this out in a personal sense over the coming years.