Interesting. Why do you think that is? I would have thought people were happier in the past than they are today.
Sorry, this was kind of a silly post lol. You're right.
Maybe because we're the only being which always wants to improve.
And when you improve, you get bored, so you want to improve again.
Of course here the term "improving" is not only economic, but also spiritual, artistic, agricultural, etc.
But you're not wrong in very particular cases, for example we could say the Internet with less social interactions, social networks, pornography, contributed to fucking up the mental health of the last generations.
Not to mention the ongoing nihilism which is clearly detrimental to mental health in some societies.