The Son Heung-min and Oh Hyeon-gyu two-top formation is a real problem because they honestly don't run enough

They don't contribute to defense and just wander around; they don't apply intense high pressing, they only pretend to do it.
If they're going to play like that, they should at least hold up the ball in attack and win aerial duels to provide some kind of return value.
Even when they scored one goal each against Ecuador, it's hard to say their performances in those two matches were actually that good.
Now that they've met teams like Uruguay and Venezuela that apply intense pressure, the lack of defensive numbers is becoming glaringly obvious.
They provide almost zero return value in attack, yet they don't contribute to defense, and when they do engage in ball battles upfront, they lose everything, whether it's aerial or ground balls.
And when a chance does come, they don't finish it with a "one shot, one kill" clinical touch.
It doesn't seem like their physical conditions are good enough to justify starting them for three consecutive matches.
It did improve slightly once the substitutes came on and started crashing into opponents and running a lot.
Lee Kang-in himself is the type with poor defensive skills, where his lack of defensive contribution is a net negative.
As a 4-4-2 winger, unless it's a game focused on attacking through penetration, he's the type who drops back to defend only to drag the ball and lose it, which isn't helpful for regaining possession in low positions, but the tactics force him into that.
Especially today, his individual form is at its worst, making it stand out even more... Using three players like Son Heung-min, Oh Hyeon-gyu, and Lee Kang-in—who either don't contribute to defense or simply lack defensive ability—together in a two-top system causes a continuous shortage of midfielders. One of them simply has to be excluded from the starting lineup.