The short answer
Almost everyone you compare yourself to is showing you a curated slice of their life — a job title, a relationship milestone, a home — while you have full, uncensored access to your own doubts, false starts, and unfinished parts. That's not a personality flaw on your end; it's a structural mismatch between what you can see of other people's lives and what you can see of your own, and it's one of the most well-documented sources of distorted self-comparison.
Comparison is automatic, not optional
Decades of research building on the original concept of social comparison have consistently found that people compare themselves to others frequently and largely automatically, especially in the absence of an objective way to judge their own progress — which describes almost every major life decision, since there's no scoreboard for "how well is my life going." Upward comparisons, made against people who appear to be doing better, are also consistently linked to feeling worse, even though people keep making them anyway, often for the very reasonable reason that they're also motivating.
Why 'figured out' specifically feels so convincing
The specific feeling of someone else being "more figured out" usually rests on visible endpoints — a wedding, a promotion, a finished renovation — rather than the actual process, which is invisible by default. Nobody posts the eighteen months of uncertainty before the decision; they post the decision. Comparing your visible uncertainty to someone else's visible resolution isn't actually a fair comparison, even though it feels like direct evidence.
What tends to help
Since the core distortion is a visibility gap rather than an actual gap in how "figured out" people are, the most useful move is usually noticing when the feeling shows up and what specifically triggered it — a person, a platform, a type of update — rather than trying to argue yourself out of the feeling in the moment, which rarely works against something this automatic.