I don't feel like I have it all per se, but I've heard some ex-peers say I do, so I feel like I can answer this.
In my case, it's mostly that a lot of people fail to realize that just because I appear otherwise well-off/functioning, I'm...really not. Yes, I do have an education and job, but a lot of people fail to realize I was practically abused and forced into keeping my education/functioning like a human being, or else the punishment I'd get would be worse than simply not "functioning" in life. The one time I wanted to stay home from school as a kid I immediately started getting treated as a servant by my parents. Even now I still get treated as an unpaid babysitter/therapist by my parents, so...
Not to mention, my family kinda falls under the typical trope of appearing like a decent one on the surface, but there's just so much fucked up shit going on behind closed doors. Parents' relationship is crumbling and they fight a lot in front of the kids, my dad threatens to ctb every so often, he also has anger issues so he could actually end up killing us instead, my mom switches between loving her kids and wanting to run away from us all every other day, so on and so forth.
In the long run, it's messed me up entirely. I have a lot of mental illnesses from how I was treated in childhood (+ other stuff that happened outside of the family), but for some reason just because I happen to, for lack of better terms, perform like a "functioning" member of society people automatically assume that my life is so much better than theirs when in reality I'm struggling a lot too. Many fail to recognize the trauma I'm still processing, the fact that I don't actually have any enjoyment in my major (and never will, no matter what major I take, because I don't get enjoyment from anything anymore), and the mental illnesses that have ruined me.
TL;DR Even if according to people I "have it all", the reality is that what I present to people is only a performance that covers up just how bad things really are when no one's looking. I'm here because there's no other opportunity (outside maybe therapy) to even say any of this to people.