Most happiness indices use flawed methodology. I wouldn't take them too seriously.

Having a child requires more planning for sure. Spontaneity is certainly fun but I do think that the ability to plan ahead is part of what rounds us out as adults.

I vibe and chill every night with my wife after the kids are asleep at 8. If we want to go out they stay with the grandparents.

Can you be as spontaneous as your were in college or as a young uncommited professional? Not really. But with a little planning you can still have your fun.

I acknowledge a lot of this comes down to finances and how functional your family is and so may not be feasible for many people. But I do want to gently push back at the idea that ideas of individuality, self-actualization etc must be deferred because of children.

You need a community to make it work and the problem is many people have less and less of that these days.