Actually I find Incheon to be one of the better airports for transit. There will always be passengers not knowing what to do. I have yet to come across any airport that has a special line for savvy passengers who know the routine. Even in the states, Pre-Check doesn't guarantee you won't get stuck behind someone who does not know how it works. If you think Incheon is bad, try making a transfer in China. You can forget about making your connnection.