Gotta say, did not know direct energy weapons were actually leaving science fiction and entering the real world yet, but it seems they're. It's obviously not star trek level, but it's way more advanced than I expected

They are, but only have a range of 1.2 miles in earth's atmosphere. Since they're on the ground, and presumably near the target (not the launcher), that means they're aimed at the warhead just before it hits the ground.

I looked up the numbers, and, interestingly, ICBMs have to slow down before they hit their target. In the midrange flight, they travel at 15,000 mph, but at re-entry the warheads are only traveling at 1900 mph, or 0.58 miles per second.

So, in the best case (the warhead is headed to the laser), the laser only gets 2.5 seconds of dwell time to intercept it. This rapidly decreases as the distance from the laser to the target increases (to 0 seconds of dwell time at 1.2 miles). Also, if the ICBM fires multiple warheads, or chaff, then you'd need to scale up the number of lasers or scale down the dwell time linearly, assuming they're all conveniently aimed within a small fraction of a mile of the laser (again, I'm assuming best-case).

Current direct energy weapons have only been demoed against UAVs, probably for this reason.

edit: my math is completely wrong: Modern nukes are optimally detonated at about 5000 ft above ground level. So, you get about 0.33 seconds of dwell time, assuming the attacker doesn't just set the warhead to detonate at a non-optimal (but still devastating) 1.2 mile altitude.

https://remm.hhs.gov/zones_nucleardetonation.htm