“especially when the people telling you this have children who have been given every advantage in the admission process” - imo, unfair comment.
Anyone can read college websites, look for what matters beyond stats. Many kids get involved in depth and breadth in legit ECs, in and out of the hs. Not just titles or things that seem glossy. Many, when given advice, consider it and review their thinking.
And anyone can google OP’s high school and learn plenty about its context, composition, goals, offerings, etc. Adcoms have the advantage of learning about thousands of high schools, have additional resources to learn about local demographics and student achievement, and travel to their areas to learn what the flavor is (in general and in specific areas.)
But no matter one’s stats, without trying to understand what the targets look for, you’re shooting in the dark. It’s not all about essays. But one’s choices through hs, all 3.5 years and through the app, say a lot about who a kid is, how he thinks, or not.
You need top performance, sure. But this isn’t a footrace where only your run that day determines your medal.