Don't forget that it's not necessarily an evolutionary disadvantage to be slightly depressed or anxious, because you tend to avoid risks. Same with low motivation and an easily distracted mind which can help to conserve energy by finding ways of avoiding tasks.
Even pre-internet, we had a rise of TV shows like "Lifestyles of the Rich and Famous" which gave viewers a daily reminder of how mediocre their lives were in comparison.
The notion that everyone's life is (or should be) full of constant excitement, joy, and amazing experiences is false. It is very one-sided. But if that's all you see of everyone else, your own troubles (which are mostly the same troubles everyone has) start to seem abnormal, something that needs to be treated. So you go see a doctor and end up medicating the problem away.
And though she's not really ill, there's a little yellow pill / She goes running for the shelter of a mother's little helper / And it helps her on her way, gets her through her busy day