You don’t need a new idea. You need a new angle on something everybody thinks they already understand.

Almost nothing is genuinely unexplored, and waiting for an untouched subject keeps you from starting. What is actually scarce is a fresh way of looking at familiar ground. Everyone has walked past the same bus stop and the same argument at home, and almost nobody has described it precisely. Your angle is the part nobody else can copy.

Take a subject that feels too ordinary to bother with and write three sentences about a detail of it nobody mentions. Keep the one that surprises you. Build the next thing you make out of that.