Why can I follow a schematic but not design a circuit?

Reading a schematic is easy because it is finished. Every line is already decided. Designing gives you a blank sheet and no one to confirm you're right. That is a different skill, not a lesser one, and not one you already own. Don't confuse the discomfort of it with proof you can't do it. Working with others can hide this problem instead of solving it. It's easy to sit in the pod and wait for someone else to draw the first block, then nod along. That is not learning to design. That is learning to follow, again, in a group instead of alone. What you need is not more theory about circuits. You already have that. You need a habit: a way to make the first mark on the blank page before you feel ready. Confidence comes after the sketch, not before it.