You're still a decade or more away from your career peak, and your physical potential is not far past its peak and declining pretty slowly for now. Feeling "old" at your age is more a matter of experience than biological fact. There are a lot of things that just aren't as exciting now because they relied heavily on novelty or just on the wonder that you could do them at all.

It's true that you've changed in a way that ruins some of the fun you used to have. None of it is new to you. You can't get hyped up for it the same way, because the sense of infinite possibility isn't there any more. Being able to do exactly what you want is no longer new and thrilling, either. And you're no longer as thrilled by inclusion and universality, reveling in those generic activities that "everybody" likes. You might not realize it yet, but you've started to choose experiences for your own sake rather than because everybody else does them.

You're hung up on this being a bad thing, but it's not really bad. I remember how excited I was as a college freshman to hike through the snow for twenty minutes to go to a house party, get wasted on beer that tasted terrible to me, and try to talk to girls that I had nothing in common with. I felt like the world was opening up to me. A year or two later, I still did it, but it wasn't an ecstatic experience anymore, because by then I knew that there was beer that actually tasted good and that the girls I really wanted to talk to were not at those parties. I could no longer feel that sense of infinite possibility. Today, I still understand why I was excited then, but I wouldn't be excited to do it now, even if I could magically pilot my younger body for a while, like Tom Hanks in Big. I remember it as a high point in my life, but what made it a high point was how excited and optimistic I felt, which only made sense in the context of my inexperience and my wonder at flexing a developing sense of autonomy.

Think of inexperience and the transition into adulthood as ingredients that made those young adult experiences delicious but which are no longer available to cook with. Doing the same things you used to enjoy in your twenties, without the inexperience and the excitement of discovering your adult autonomy, is like eating french fries without salt, or salad without dressing, a joyless chore. Don't try to force it.

Would you order curry at a restaurant that only had tomatoes, basil, oregano, and olive oil in the kitchen? If you went to a bakery for chocolate-chip cookies, and they said sorry, we're all out of chocolate and sugar, would you insist on them baking a batch for you with what they had? Don't get hung up on the stuff you used to enjoy.

You have new ingredients to work with, ingredients that are particular to you and your experience. They aren't so universal that "everybody" your age will enjoy the same things, but not so unique that you'll be alone. You need to start to figure out the flavor profile for this time in your life. If you don't know where to start, start anywhere. Look around, try whatever looks good, and if nothing looks good yet, try things at random while you're looking. It won't all taste good. That's life.