Here's the current status:
|Naver's info box for Incheon Airport congestion status (desktop view)|
I guess the point is that you can judge the level of congestion at the airport beforehand. It lists up there the total number of people and ranks it. In that image you can see it currently at "원활" or a smooth/seamless degree, a.k.a. no congestion, no heavy lines, etc. So you can check ahead of time and know if you need to leave your home much earlier, or can afford some time to spare for those extra twenty minutes of LoL.
I can't really see this being useful for average trips, but it could be handy for high travel days, like this past week's summer vacation time, when the airport looked like this:
|A packed Incheon Airport on July 31, 2016. Image: Instiz|
On that day, the status looked like this:
|Naver's info box for Incheon Airport congestion status (mobile view)|
To see it for yourself, search Naver for 인천공항 출국장 혼잡도 or click here.