All this is just saying that you personally put more weight on the things that are better about later adulthood than early adulthood or adolescence. And that can be your choice, but it doesn't have to be everyone's choice.

You acknowledge that the health and friendships piece gets harder with age but push back against the idea that it inevitably gets worse. But averaged among all people, things will tend to get worse, and some people who actually experience that deterioration will conclude (as is their right) that things were better when health and friendships were easier.

But we also make new relationships as we get older. Is life better when you have a grandparent? Or when you have a grandchild?

These aren't symmetrical. When you are a young person who loves your grandparents, you haven't actually mourned a loss of a grandchild you personally knew. On the flip side, when you have a grandchild you might also view that relationship through the lens of a lost relationship with a deceased grandparent. In other words, only one of those experiences is 100% good, rather than a bittersweet mix of good and sad.

Not to mention, plenty of people will never have grandchildren. To them, the mourned loss of a grandparent is the end of that road. There's no replacement on its way.

Put it this way: if given the opportunity to wake up 10 years in the past, in your body of 10 years ago, how positive or negative would you view that? Plenty of people would vote on different sides of that, and that's OK to have different views based on one's own experiences.