Well, yeah. Like the man literally said, the original designers of the weapon have far more powerful power sources. It’s supposed to have rapid-fire, but the Parpaldians are trying to power it with a power plant far weaker than it was designed for, and they even had to hack together certain parts that they failed to smuggle in.That laser cannon does not look like it is designed for anti air, unless the laser can stay on several seconds and it can move rapidly making it a CIWS. Generally you want rapid and/or wide fire for anti air, something like a rail gun mostly only works for the first shot unless it has amazing tracking.
That's what it looks like, but even some basic evasive maneuvers while uncertain about where the railgun is would be quite effective at avoiding getting hit unless it could be aimed quite quickly. A glance at it, even considering it to be roughly recreated, makes it look like it would be too slow to adjust for aircraft. It looks for it to be used against aircraft they would aim in front of the flight path and fire when the target crosses the crosshair. So once they snipe the first target and announce they are firing at them, they would need to be very lucky to hit another target once they are being cautious.It's probably designed to detect and shoot down aircraft long before they can detect the railgun targeting it, dozens of miles away like Stonehenge in Ace Combat 4.