I grew up poor in the south. I built a pretty okay career, primarily in D.C. Over the last few years, my visits home have had a similar feeling.
For me, it's not just seeing everyone age, but seeing how they've chosen to "settle" in many ways. There's a realization that many family members have developed as much as they ever will. When I was young, it was possible to imagine myself as a "temporarily embarrassed millionaire." One day, I'd be able to come back and just fix it all for everyone, if I were successful enough. Now I increasingly see the absurdity of that thinking. It's a struggle. It's likely to continue to be a struggle. Many have already gone--so much for helping them have things a little easier. It's utterly unfair. And you're more painfully aware of those realities through adult eyes.
Beyond that, a childhood home is a complex thing. I have many positive memories of the place, but I have many really dark memories that also hang over the same place. Those are things I didn't wrestle with until I got older, which partially accounts for the change in feeling.
The bright side for me is that, despite all of this, I have started to see a more full picture of where I grew up. For years, I could only see the bad, but having dealt with that a little better by now, I can begin to appreciate its charms. It has started to lend a mystique to a place I thought could never rise above humdrum, at best.