It sounds as if you’re already dealing with your feelings in many productive ways, and they just haven’t delivered results. Yet.
That doesn’t mean they won’t. It can take time for the dividends of your choices to become clear to you. For one, I think they’re being obscured by the newness of this phase of life for your peers — and the fact that each is traditionally launched with a party. When you’re in the flurry of weddings, showers, housewarmings, etc. — and it is typically a flurry — you’re seeing many people who are at the height of their joy with these milestones.
I don’t mean to sound cynical, just realistic — some of these marriages will unravel; some of these houses will be money pits; some of these kids will be difficult and wear out their parents, who will love them nonetheless but who will give up a lot of other valued things to make it all work. The highs and comforts inherent in marriage/house/kiddos are real and significant, but so are the lows, and the mehs.
And this will become steadily more apparent to you as your friends and family get beyond the cake-and-gifts phase, and celebration mode gives way to the rigors of daily life. (If we had showers and receptions for singleton milestones instead, would the jealousy jump sides? Discuss.)
This will happen, possibly, as your “new/fun” activities and travels evolve into deeper commitments and pleasures.