If the premise of the defense shield is that it can dissipate a certain amount of energy by distributing the energy across its whole, why doesn't throwing more

If the premise of the defense shield is that it can dissipate a certain amount of energy by distributing the energy across its whole, why doesn't throwing more explosives makes sense? Presumably the people doing weapons design in this fantasy setting have at least as much sense as we do now. This means a ship colliding holding weapons are unlikely to detonate completely (not armed) and thus not deal a ton of damage. This movie is set in a universe where less than 20 years ago, fully automated machines nearly destroyed those who remain. Both the complexity of a firing solution in space as well as explicit non-automation of some things rather easily suffice as reasons for a delay. This discounts surprise coupletely. I don't know much about magic space lasers, but I'm also willing to suspend disbelief enough to allow they have a limited range of effectiveness. If you wanted to make random technical arguments, I'd have imagined that "pew pew" sounds in space is where you would start.