Why do I freeze when asked how it all fits together?

You can take a ticket and build exactly what it describes. Hand you a whole system — a dozen services, no clear edges, three teams with opinions — and something in you locks shut. You wait for someone else to speak first. That freeze is not proof you're missing the gift for this work. It's proof you're skipping a step. You try to produce the final answer before you've cut the mess into pieces you can actually hold. No one holds a whole system in their head at once. Not you, not the senior engineer you compare yourself to in that meeting. Your team feels this too — even the ones who talk first. Often they are guessing out loud, not seeing clearly, and the room mistakes their speed for sight. The fix is not more confidence. It is a method, practiced together, out loud, one piece at a time.