Are your 20s really the "best years" of your life? Why do people say that?

I've heard people say countless times that your 20s are supposed to be the best years of your life. But why is that? What is it about being in your 20s that makes them so "special"? And how much truth is there to that idea? I get that in your 20s, you’re often more carefree, you have fewer responsibilities, maybe more energy, and society generally expects you to be exploring life and making mistakes. But what about the years after? Why do people act like your 30s, 40s, or any age after that isn't as fun, youthful, or exciting? Is it really downhill after your 20s, or is that just a stereotype we’ve been sold? Can't we continue to enjoy life in new ways as we get older? For those who've passed their 20s, how has your life changed? Is it harder to have fun, or is it just different? Can life in your 30s and beyond be just as good (or better)? Or do we face more limitations as time goes on, making it harder to experience that same excitement and freedom? I’m curious if this idea that your 20s are the peak of life is valid or if we can make the later stages of life just as fulfilling. What do you think?