Success for a social network is not "people feeling better on average" it's people coming back more often on average. Their actual level of enjoyment or well-being is irrelevant to the platform.
A social network's ideal audience would be a group of people who are relatively discontent with their lives and provide a series of small improvements to that state of being, but ones that quickly fade, and then encourage them to repeat that cycle as often as possible. That way the susceptibility to advertising remains high and boosts advertiser ROI, which raises the social network's value as a platform.
Come to think of it, that sounds pretty familiar.
I've never used Instagram much, but that sounds like one aspect of that network I've read about. Everyone curates their profile to make their lives seem more fun and more interesting than they really are, often with a materialist angle. The real you looks inadequate compared to these false lives, leaving many feeling insecure about themselves. Then you have professional "influencers" with hyper-curated profiles that depict a fantastically fun and fashionable life. They make money by shilling products that subtly promise to let you join in on that lifestyle, if you only buy.
Its just that, Instagram especially because of the power of an image, its like not only did they set out to create a platform to maximize your insecurity, they recruited thousands of people and gave them a special title ("influencer") and pay them to amplify that message as loudly as possible, then bake in the same addictive interactions as Facebook, and then monetized the whole thing.
Its not to say that its always bad and should be shut down, just be aware of the effects it can have and be honest about how you react to them.
I mean they might really want you to, but they don't put apps on your phone and reset your privacy settings to let them reach out to you and spam you with notifications through multiple channels (email/text/sms) multiple times per day trying to get you to engage that are endlessly optimized by very smart people to trigger that engagement, not a lot, but just a hit to get you coming back for more.
And then grow into one of the largest companies in America lead by one of richest men in America by leveraging the addicting and repetitive nature of that activity to literally and intentionally monetize _their_ influence how _you_ think (advertising).
Sorry, but what is going on right now @ Facebook can't be hand waved away by saying that humans are social animals.
But I see your point in that FB's management isn't really pushing to make those sort of interactions happen more frequently, they're just trying to get people to spend as much time on it as possible to extract ad money from them.
You seem to be using it in a responsible way, don't let anyone judge you for that.
Just be aware of the forces arrayed against you and be honest about how it effects you. If you find yourself not enjoying it or see it have a negative effect on your loved ones, try to cut back. If you have no problem doing so, then there's nothing to worry about, but if you do find it difficult then you know you may have a problem.
Honestly, I expect within the year we'll see the first nationwide support groups for social media addiction a.l.a Alcoholics Anonymous. If no one has done a startup yet for an app that is designed to help, that would be a great opportunity.