Yep.
It could only kill missiles in the boost phase, when they’re the most vulnerable. That required the modified 747 to run a very predicatable racetrack pattern along the FEBA or hostile border.
Although, the variable cost of a laser firing (especially a solid-state laser) is signicicantly less than a guided missile. So, you might have a higher fixed cost and overhead, but much smaller variable costs per kill.
Between 1996 and 2004, the Army’s Theater High Energy laser (THEL) project out of Huntsville Alabama was shooting down inbound rockets with a liquid-fueled high energy laser.
The THEL looked much like a 30 inch diameter searchlight, also mounted on top of a “trailer-like” portable shipping container. The laser liquid fuel was in pressurized H2O2 and other tanks, also containerized.
So, of course, if I were opposing this system, first thing I’d do would be dropping a couple of dozen “dumb” mortar rounds .... on top of the radar. 8<)
It was still good that we developed the weapons, even if they didn’t prove practical. We came up with some innovations that we can use in astronomy and other applications, which we might not have discovered without all that fat federal funding chasing a weapons system :)